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List: qgis-user
Subject: Re: [Qgis-user] Qgis-user Layer question
From: Jonathan Webb <jonathan () jwebbgis ! co ! uk>
Date: 2015-07-31 6:44:41
Message-ID: D5719F82-7B02-4086-881F-9F33CAB5B720 () jwebbgis ! co ! uk
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I've converted road polylines to polygons before by buffering. You may have to do \
different road grades/widths in several stages.
On 31 July 2015 05:39:15 BST, qgis-user-request@lists.osgeo.org wrote:
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> ------------------------------------------------------------------------
>
> Today's Topics:
>
> 1. Layer question (Shane)
> 2. Re: Layer question (Tom Lennon)
> 3. Re: Layer question (Bernd Vogelgesang)
> 4. Re: Layer question (Nicolas Cadieux)
> 5. Re: How to convert raster routes into vector format?
> (Nick Papadonis)
> 6. Raster Calculator Expression to determine color (Nick Papadonis)
> 7. Re: Raster Calculator Expression to determine color (Nyall Dawson)
> 8. Re: Raster Calculator Expression to determine color
> (Nick Papadonis)
> 9. Re: Raster Calculator Expression to determine color
> (Nick Papadonis)
> 10. Re: Raster Calculator bug? (Nick Papadonis)
>
>
> ------------------------------------------------------------------------
>
> From: Shane <shaned173@gmail.com>
> To: qgis-user@lists.osgeo.org
> Sent: Thu Jul 30 20:05:09 BST 2015
> Subject: [Qgis-user] Layer question
>
> Hi group,
>
> I have a layer with roads which are lines having a style of gray
> with thin black outlines on either side. Another layer (parking lots)
> has polygons having the same color as the roads but not outlined. The
> parking lot layer is above the road layer in rendering order. So road
> outlines are hidden by the parking lot layer when a parking lot
> intersects a road.
>
> Here's the trouble - having parking lots with no outline, but roads
> with outlines looks odd. Is there some way to have the outlines of
> both
> road and parking lot layers removed from rendering when these two
> features cross?
>
> One method I've considered is to draw the roads and parking lots as
> polygons in the same layer? It would make drawing the roads
> non-trivial, but the problem with outlines would be eliminated.
>
> Shane
>
>
>
>
> ------------------------------------------------------------------------
>
> From: Tom Lennon <tolennon@gmail.com>
> To: Shane <shaned173@gmail.com>
> Cc: qgis-user <qgis-user@lists.osgeo.org>
> Sent: Thu Jul 30 22:11:17 BST 2015
> Subject: Re: [Qgis-user] Layer question
>
> Hi Shane:
> Have you tried moving the parking lot layer to below the road layer?
> That way roads over parking lots would always show.
>
> Tom
>
> On Thu, Jul 30, 2015 at 3:05 PM, Shane <shaned173@gmail.com> wrote:
>
> > Hi group,
> >
> > I have a layer with roads which are lines having a style of gray
> with
> > thin black outlines on either side. Another layer (parking lots) has
> > polygons having the same color as the roads but not outlined. The
> parking
> > lot layer is above the road layer in rendering order. So road
> outlines are
> > hidden by the parking lot layer when a parking lot intersects a road.
> >
> > Here's the trouble - having parking lots with no outline, but
> roads
> > with outlines looks odd. Is there some way to have the outlines of
> both
> > road and parking lot layers removed from rendering when these two
> features
> > cross?
> >
> > One method I've considered is to draw the roads and parking lots
> as
> > polygons in the same layer? It would make drawing the roads
> non-trivial,
> > but the problem with outlines would be eliminated.
> >
> > Shane
> >
> > _______________________________________________
> > Qgis-user mailing list
> > Qgis-user@lists.osgeo.org
> > http://lists.osgeo.org/mailman/listinfo/qgis-user
> >
>
>
>
> --
> tolennon@gmail.com
>
>
> ------------------------------------------------------------------------
>
> From: Bernd Vogelgesang <bernd.vogelgesang@gmx.de>
> To: qgis-user@lists.osgeo.org
> Sent: Thu Jul 30 22:50:36 BST 2015
> Subject: Re: [Qgis-user] Layer question
>
> Hi Shane,
> I think without a screenshot, we have no chance to really get an idea
> what
> it's all about.
> Best to use a service like http://imgur.com/ and post the link cause
> the
> list will bounce too heavy attachments.
>
> Bernd
>
>
>
> Am 30.07.2015, 23:11 Uhr, schrieb Tom Lennon <tolennon@gmail.com>:
>
> > Hi Shane:
> > Have you tried moving the parking lot layer to below the road layer?
> > That way roads over parking lots would always show.
> >
> > Tom
> >
> > On Thu, Jul 30, 2015 at 3:05 PM, Shane <shaned173@gmail.com> wrote:
> > > Hi group,
> > >
> > > I have a layer with roads which are lines having a style of gray
> with
> > > thin black outlines on either side. Another layer >>(parking lots)
> has
> > > polygons having the same color as the roads but not outlined. The
> > > parking lot layer is above the road layer in >>rendering order. So
>
> > > road outlines are hidden by the parking lot layer when a parking lot
>
> > > intersects a road.
> > >
> > > Here's the trouble - having parking lots with no outline, but
> roads
> > > with outlines looks odd. Is there some way to have the >>outlines
> of
> > > both road and parking lot layers removed from rendering when these
> two
> > > features cross?
> > >
> > > One method I've considered is to draw the roads and parking lots
> as
> > > polygons in the same layer? It would make drawing the >>roads
> > > non-trivial, but the problem with outlines would be eliminated.
> > >
> > > Shane
> > >
> > > _______________________________________________
> > > Qgis-user mailing list
> > > Qgis-user@lists.osgeo.org
> > > http://lists.osgeo.org/mailman/listinfo/qgis-user
> >
> >
> >
> > --tolennon@gmail.com
>
>
>
> --
> Bernd Vogelgesang
> Siedlerstraße 2
> 91083 Baiersdorf/Igelsdorf
> Tel: 09133-825374
>
> ------------------------------------------------------------------------
>
> From: Nicolas Cadieux <nicolas.cadieux@archeotec.ca>
> To: qgis-user@lists.osgeo.org
> Sent: Thu Jul 30 23:07:50 BST 2015
> Subject: Re: [Qgis-user] Layer question
>
> Hi,
> You can play with the layer blending. You can use "multiply" ,
> "add", "subtract"... (something like that, I am not in front of a
> computer). There are also the same blending options in the vector
> object styling so that you can select what happens when two objects
> intersect in the same layer.
> Maybe that could help?
> Nicolas Cadieux M.Sc.
> Les Entreprises Archéotec inc. 
> 8548, rue Saint-Denis Montréal H2P 2H2
> Téléphone: 514.381.5112  Fax: 514.381.4995
> www.archeotec.ca
> On Jul 30, 2015 5:45 PM, "berndv. [via OSGeo.org]"
> <ml-node+s1560n5217887h58@n6.nabble.com> wrote:
>
>
>
>
> Hi Shane, I think without a screenshot, we have no chance to really get
> an idea what it's all about. Best to use a service like
> http://imgur.com/ and post the link cause the list will bounce too
> heavy attachments. Bernd Am 30.07.2015, 23:11 Uhr, schrieb Tom Lennon
> < [hidden email] >: <blockquote style="border-left:2px
> solid #cccccc;padding:0 1em" style="margin:0 0
> 0.8ex;border-left:#0000ff 2px solid;padding-left:1ex"> Hi
> Shane: Have you tried moving the parking lot layer to below the road
> layer? That way roads over parking lots would always show. Tom On Thu,
> Jul 30, 2015 at 3:05 PM, Shane < [hidden email] > wrote:
> <blockquote style="border-left:2px solid #cccccc;padding:0
> 1em" style="margin:0 0 0 0.8ex;border-left:1px #ccc
> solid;padding-left:1ex"> Hi group,
>
> I have a layer with roads which are lines having a style of gray
> with thin black outlines on either side. Another layer (parking lots)
> has polygons having the same color as the roads but not outlined. The
> parking lot layer is above the road layer in rendering order. So road
> outlines are hidden by the parking lot layer when a parking lot
> intersects a road.
>
> Here's the trouble - having parking lots with no outline, but
> roads with outlines looks odd. Is there some way to have the outlines
> of both road and parking lot layers removed from rendering when these
> two features cross?
>
> One method I've considered is to draw the roads and parking lots
> as polygons in the same layer? It would make drawing the roads
> non-trivial, but the problem with outlines would be eliminated.
>
> Shane
>
> _______________________________________________
> Qgis-user mailing list
> [hidden email]
> http://lists.osgeo.org/mailman/listinfo/qgis-user
> -- [hidden email]
>
> -- Bernd Vogelgesang Siedlerstraße 2 91083 Baiersdorf/Igelsdorf Tel:
> 09133-825374 _______________________________________________
> Qgis-user mailing list
> [hidden email]
> http://lists.osgeo.org/mailman/listinfo/qgis-user
>
>
>
>
>
>
>
>
> If you reply to this email, your message will be added to the
> discussion below:
> http://osgeo-org.1560.x6.nabble.com/Layer-question-tp5217849p5217887.html
>
>
>
> To start a new topic under Quantum GIS - User, email
> ml-node+s1560n4125267h38@n6.nabble.com
> To unsubscribe from Quantum GIS - User, click here .
> NAML
>
>
>
>
> --
> View this message in context:
> http://osgeo-org.1560.x6.nabble.com/Layer-question-tp5217849p5217890.html
> Sent from the Quantum GIS - User mailing list archive at Nabble.com.
>
> ------------------------------------------------------------------------
>
> From: Nick Papadonis <npapadonis@gmail.com>
> To: "Håvard Tveite" <havard.tveite@nmbu.no>
> Cc: qgis-user@lists.osgeo.org
> Sent: Fri Jul 31 00:45:56 BST 2015
> Subject: Re: [Qgis-user] How to convert raster routes into vector
> format?
>
> Hi Havard,
>
> Unfortunately, the expression below results in a complete black TIFF.
> I am referencing the correct layer. Any ideas?
>
> Thanks
> Nick
>
> > On Jul 29, 2015, at 4:34 PM, Håvard Tveite <havard.tveite@nmbu.no>
> wrote:
> >
> > With QGIS 2.10, the following should work (probably also OK
> > for earlier versions).
> >
> > Check the band values of your colour using the info button,
> > and use the values in the expression below (assuming the
> > name of your raster layer is yourraster) instead of 116, 20
> > and 31:
> >
> > ("yourraster@1" = 116 AND "yourraster@2" = 20 AND "yourraster@3" =
> 31) * 1
> >
> > This should give you a binary raster with 1 in the pixels
> > that have your colour and 0 in the pixels with other colours.
> >
> > In the style dialogue you can use the following to see the
> > resulting binary image:
> > Colour gradient: "white to black"
> > Min: 0
> > Max: 1
> >
> > You should be able to use r.thin on that image, but I am not
> > able to test this now, as I am on Ubuntu, and have not been
> > able to get GRASS to work through Processing on that platform
> > for QGIS 2.10.
> >
> > Håvard
> >
> > On 29. juli 2015 16:40, Nick Papadonis wrote:
> > > Hi Håvard,
> > >
> > > I found the raster calculator and read the online manual for it,
> however am still a bit lost. I was also playing with the Style
> properties and color bands last night to try to accomplish this. I was
> unable to get a single binary image with the single color (red in this
> case). I think the understand the r.thin suggestion and that it will
> thin the single color thick lines for vectorization. Appreciate if you
> can expand on obtaining a binary skeleton of the one color of the
> trails.
> > >
> > > Thanks again,
> > > Nick
> > >
> > > > On Jul 29, 2015, at 7:18 AM, Havard Tveite <havard.tveite@nmbu.no>
> wrote:
> > > >
> > > > If you are going to use GRASS r.to.vect (for instance through QGIS
> > > > Processing), you will need a binary skeleton image.
> > > > You could get one by using the raster calculator to extract
> > > > your single colour as a binary image, and then GRASS r.thin
> > > > (available in QGIS Processing) to get the skeleton.
> > > >
> > > > Håvard
> > > >
> > > > On 29/7/2015 8:36:AM, Nick Papadonis wrote:
> > > > > Hi Folks,
> > > > >
> > > > > I have a map with numerous trails in a single color and would like
> to vectorize these. Is there a mode Qgis can be placed in such that a
> color can be selected for inclusion in the vectorization process? I.e.
> to make converting these routes to vector format easier?
> > > > >
> > > > > Thanks again
> > > > > _______________________________________________
> > > > > Qgis-user mailing list
> > > > > Qgis-user@lists.osgeo.org
> > > > > http://lists.osgeo.org/mailman/listinfo/qgis-user
> > > > >
> > >
>
>
>
>
> ------------------------------------------------------------------------
>
> From: Nick Papadonis <npapadonis@gmail.com>
> To: Qgis-user@lists.osgeo.org
> Sent: Fri Jul 31 02:07:44 BST 2015
> Subject: [Qgis-user] Raster Calculator Expression to determine color
>
> HI Folks,
>
> I'm trying to use the following expression to pick up the red colored
> routes on a map in which I used the info pointer tool to get the band
> values for the color.
>
> ("m@1" < 238 AND "m@1" > 213 AND "m@2" < 123 AND "m@2" > 98 AND "m@3" <
> 125 AND "m@3" < 99) * 1
>
> Unfortunately, when this expression is used the resulting map is black
> with no other pixels for the detected color.
>
> If I break down this expression to a simple "greater than" line for
> single band, then things work.
>
> Does anyone know where this expression needs to be corrected?
>
> Thanks again,
> Nick
>
>
> ------------------------------------------------------------------------
>
> From: Nyall Dawson <nyall.dawson@gmail.com>
> To: Nick Papadonis <npapadonis@gmail.com>
> Cc: Qgis-user@lists.osgeo.org
> Sent: Fri Jul 31 02:29:34 BST 2015
> Subject: Re: [Qgis-user] Raster Calculator Expression to determine
> color
>
> On 31 Jul 2015 11:07 am, "Nick Papadonis" <npapadonis@gmail.com> wrote:
> >
> > HI Folks,
> >
> > I'm trying to use the following expression to pick up the red colored
> routes on a map in which I used the info pointer tool to get the band
> values for the color.
> >
> > ("m@1" < 238 AND "m@1" > 213 AND "m@2" < 123 AND "m@2" > 98 AND "m@3"
> <
> 125 AND "m@3" < 99) * 1
>
> Should that last check be "m@3" > 99?
>
> Nyall
>
> >
> > Unfortunately, when this expression is used the resulting map is
> black
> with no other pixels for the detected color.
> >
> > If I break down this expression to a simple "greater than" line for
> single band, then things work.
> >
> > Does anyone know where this expression needs to be corrected?
> >
> > Thanks again,
> > Nick
> > _______________________________________________
> > Qgis-user mailing list
> > Qgis-user@lists.osgeo.org
> > http://lists.osgeo.org/mailman/listinfo/qgis-user
>
>
> ------------------------------------------------------------------------
>
> From: Nick Papadonis <npapadonis@gmail.com>
> To: Nyall Dawson <nyall.dawson@gmail.com>
> Cc: Qgis-user@lists.osgeo.org
> Sent: Fri Jul 31 02:30:44 BST 2015
> Subject: Re: [Qgis-user] Raster Calculator Expression to determine
> color
>
>
> > On Jul 30, 2015, at 9:29 PM, Nyall Dawson <nyall.dawson@gmail.com>
> wrote:
> >
> >
> > On 31 Jul 2015 11:07 am, "Nick Papadonis" <npapadonis@gmail.com
> <mailto:npapadonis@gmail.com>> wrote:
> > >
> > > HI Folks,
> > >
> > > I'm trying to use the following expression to pick up the red
> colored routes on a map in which I used the info pointer tool to get
> the band values for the color.
> > >
> > > ("m@1" < 238 AND "m@1" > 213 AND "m@2" < 123 AND "m@2" > 98 AND
> "m@3" < 125 AND "m@3" < 99) * 1
> >
> > Should that last check be "m@3" > 99?
> >
> >
> Yeah, I changed that and still same results. If I specify on > and
> remove the < expressions, then everything works. Very odd considering
> the color is within the range above (with the line you referenced
> fixed).
>
> Thanks
> > Nyall
> >
> > >
> > > Unfortunately, when this expression is used the resulting map is
> black with no other pixels for the detected color.
> > >
> > > If I break down this expression to a simple "greater than" line for
> single band, then things work.
> > >
> > > Does anyone know where this expression needs to be corrected?
> > >
> > > Thanks again,
> > > Nick
> > > _______________________________________________
> > > Qgis-user mailing list
> > > Qgis-user@lists.osgeo.org <mailto:Qgis-user@lists.osgeo.org>
> > > http://lists.osgeo.org/mailman/listinfo/qgis-user
> <http://lists.osgeo.org/mailman/listinfo/qgis-user>
>
>
> ------------------------------------------------------------------------
>
> From: Nick Papadonis <npapadonis@gmail.com>
> To: Nyall Dawson <nyall.dawson@gmail.com>, Qgis-user@lists.osgeo.org
> Sent: Fri Jul 31 02:56:24 BST 2015
> Subject: Re: [Qgis-user] Raster Calculator Expression to determine
> color
>
>
> > On Jul 30, 2015, at 9:29 PM, Nyall Dawson <nyall.dawson@gmail.com>
> wrote:
> > On 31 Jul 2015 11:07 am, "Nick Papadonis" <npapadonis@gmail.com
> <mailto:npapadonis@gmail.com>> wrote:
> > >
> > > HI Folks,
> > >
> > > I'm trying to use the following expression to pick up the red
> colored routes on a map in which I used the info pointer tool to get
> the band values for the color.
> > >
> > > ("m@1" < 238 AND "m@1" > 213 AND "m@2" < 123 AND "m@2" > 98 AND
> "m@3" < 125 AND "m@3" < 99) * 1
> >
> > Should that last check be "m@3" > 99?
> >
> >
>
> I corrected above to:
> ("m@1" < 238 AND "m@1" > 213 AND "m@2" < 123 AND "m@2" > 98 AND "m@3" <
> 125 AND "m@3" > 99) * 1
>
> with the same results which is black output tiff.
>
> I then tried individual expressions for each band as separate steps
> (sanity check):
> ("m@1" < 238 AND "m@1" > 213) * 1
> ("m@2" < 123 AND "m@2" > 98) * 1
> ("m@3" < 125 AND "m@3" > 99) * 1
>
> These all produce a masked image, however masked incorrectly because
> I'm evaluating only a single band in the Raster Calculator.
>
> When I combine evaluation of bands as above or below to pick pixels in
> color range:
>
> (("m@1" < 238 AND "m@1" > 210) AND ("m@2" < 123 AND "m@2" > 94) AND
> ("m@3" < 130 AND "m@3" > 98)) * 1
>
> I get a black image with no matches. I expected at least one pixel
> identified using this expression because I evaluate a pixel at 224,
> 108, 115 and there are many other pixels in above range.
>
> Does anyone know if my expression needs correction or the Raster
> Calculator can only evaluate a single band in the expression?
>
> Thanks again,
> Nick
>
> > Nyall
> >
> > >
> > > Unfortunately, when this expression is used the resulting map is
> black with no other pixels for the detected color.
> > >
> > > If I break down this expression to a simple "greater than" line for
> single band, then things work.
> > >
> > > Does anyone know where this expression needs to be corrected?
> > >
> > > Thanks again,
> > > Nick
> > > _______________________________________________
> > > Qgis-user mailing list
> > > Qgis-user@lists.osgeo.org <mailto:Qgis-user@lists.osgeo.org>
> > > http://lists.osgeo.org/mailman/listinfo/qgis-user
> <http://lists.osgeo.org/mailman/listinfo/qgis-user>
>
>
> ------------------------------------------------------------------------
>
> From: Nick Papadonis <npapadonis@gmail.com>
> To: Qgis-user@lists.osgeo.org
> Sent: Fri Jul 31 05:39:12 BST 2015
> Subject: Re: [Qgis-user] Raster Calculator bug?
>
> Folks,
>
> I'm using QGIS 10.1. The following expressions result in a black
> raster of 0's, when I expected only red pixels to appears in the binary
> image indicating routes on a map:
>
> a) ("m@1" < 238 AND "m@1" > 213 AND "m@2" < 123 AND "m@2" > 98 AND
> "m@3" < 125 AND "m@3" > 99) * 1
> b) (("m@1" < 238 AND "m@1" > 210) * 1) * (("m@2" < 123 AND "m@2" > 94)
> * 1) * (("m@3" < 130 AND "m@3" > 98) * 1)
>
> I then tried the following individual expressions for each band as
> separate steps (sanity check) and they work to cover the pixels in
> range:
> c) ("m@1" < 238 AND "m@1" > 213) * 1
> d) ("m@2" < 123 AND "m@2" > 98) * 1
> e) ("m@3" < 125 AND "m@3" > 99) * 1
>
> I then tried the following expression which appears to create a proper
> greyscale image focusing on the red pixels. I replaced the
> multiplication with addition to see what was happening:
> f) (("m@1" < 238 AND "m@1" > 210) * 1) + (("m@2" < 123 AND "m@2" > 94)
> * 1) + (("m@3" < 130 AND "m@3" > 98) * 1)
>
> The resulting raster has a Min = 0 and Max = 1.998. I was expecting it
> to be Min = 0 and Max = 3. The value of 3 would indicate all 3 bands
> were positive on color match. I then go to the layer properties and
> load calculate min/max again and it is Min = 0 and Max = 3. I tried to
> change the min/max settings on they layer and these settings will not
> stay set. The layer goes back to Max = 1.998. What's even more odd is
> the max being a floating point number. I suspect that may be part of
> the issue. Anyone know why this is the case for integer band values?
> Has anyone successfully used the Raster Calculator to perform this sort
> of work before?
>
> Thanks again,
> Nick
>
>
> ------------------------------------------------------------------------
>
> _______________________________________________
> Qgis-user mailing list
> Qgis-user@lists.osgeo.org
> http://lists.osgeo.org/mailman/listinfo/qgis-user
--
Jonathan Webb
Freelance GIS specialist
07941 921905
www.jwebbgis.co.uk
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/></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; \
-webkit-line-break: after-white-space;" class="">I've converted road polylines to \
polygons before by buffering. You may have to do different road grades/widths in \
several stages. <br><br><div class="gmail_quote">On 31 July 2015 05:39:15 BST, \
qgis-user-request@lists.osgeo.org wrote:<blockquote class="gmail_quote" \
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your Subject line so it is more specific<br />than "Re: Contents of Qgis-user \
digest..."<br /></pre><p style="margin-top: 2.5em; margin-bottom: 1em; border-bottom: \
1px solid #000"></p><pre class="k9mail">Today's Topics:<br /><br /> 1. Layer \
question (Shane)<br /> 2. Re: Layer question (Tom Lennon)<br /> 3. Re: Layer \
question (Bernd Vogelgesang)<br /> 4. Re: Layer question (Nicolas Cadieux)<br /> \
5. Re: How to convert raster routes into vector format?<br /> (Nick \
Papadonis)<br /> 6. Raster Calculator Expression to determine color (Nick \
Papadonis)<br /> 7. Re: Raster Calculator Expression to determine color (Nyall \
Dawson)<br /> 8. Re: Raster Calculator Expression to determine color<br /> \
(Nick Papadonis)<br /> 9. Re: Raster Calculator Expression to determine color<br /> \
(Nick Papadonis)<br /> 10. Re: Raster Calculator bug? (Nick Papadonis)<br /></pre><p \
style="margin-top: 2.5em; margin-bottom: 1em; border-bottom: 1px solid \
#000"></p><table style="border: 0"><tbody><tr><th style="text-align: left; \
vertical-align: top;">From:</th><td>Shane <shaned173 \
gmail.com="gmail.com"></shaned173></td></tr><tr><th style="text-align: left; \
vertical-align: top;">To:</th><td>qgis-user@lists.osgeo.org</td></tr><tr><th \
style="text-align: left; vertical-align: top;">Sent:</th><td>Thu Jul 30 20:05:09 BST \
2015</td></tr><tr><th style="text-align: left; vertical-align: \
top;">Subject:</th><td>[Qgis-user] Layer question</td></tr></tbody></table><pre \
class="k9mail"> Hi group,<br /><br /> I have a layer with roads which are lines \
having a style of gray <br />with thin black outlines on either side. Another layer \
(parking lots) <br />has polygons having the same color as the roads but not \
outlined. The <br />parking lot layer is above the road layer in rendering order. \
So road <br />outlines are hidden by the parking lot layer when a parking lot <br \
/>intersects a road.<br /><br /> Here's the trouble - having parking lots with no \
outline, but roads <br />with outlines looks odd. Is there some way to have the \
outlines of both <br />road and parking lot layers removed from rendering when these \
two <br />features cross?<br /><br /> One method I've considered is to draw the \
roads and parking lots as <br />polygons in the same layer? It would make drawing \
the roads <br />non-trivial, but the problem with outlines would be eliminated.<br \
/><br /> Shane<br /><br /><br /></pre><p style="margin-top: 2.5em; margin-bottom: \
1em; border-bottom: 1px solid #000"></p><table style="border: 0"><tbody><tr><th \
style="text-align: left; vertical-align: top;">From:</th><td>Tom Lennon <tolennon \
gmail.com="gmail.com"></tolennon></td></tr><tr><th style="text-align: left; \
vertical-align: top;">To:</th><td>Shane <shaned173 \
gmail.com="gmail.com"></shaned173></td></tr><tr><th style="text-align: left; \
vertical-align: top;">Cc:</th><td>qgis-user <qgis-user \
lists.osgeo.org="lists.osgeo.org"></qgis-user></td></tr><tr><th style="text-align: \
left; vertical-align: top;">Sent:</th><td>Thu Jul 30 22:11:17 BST \
2015</td></tr><tr><th style="text-align: left; vertical-align: \
top;">Subject:</th><td>Re: [Qgis-user] Layer question</td></tr></tbody></table><div \
dir="ltr"><div class="gmail_default" style="font-size:small">Hi Shane:</div><div \
class="gmail_default" style="font-size:small">Have you tried moving the parking lot \
layer to below the road layer?</div><div class="gmail_default" \
style="font-size:small">That way roads over parking lots would always show.</div><div \
class="gmail_default" style="font-size:small"><br /></div><div class="gmail_default" \
style="font-size:small">Tom</div></div><div class="gmail_extra"><br /><div \
class="gmail_quote">On Thu, Jul 30, 2015 at 3:05 PM, Shane <span dir="ltr"><<a \
href="mailto:shaned173@gmail.com" target="_blank">shaned173@gmail.com</a>></span> \
wrote:<br /><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px \
#ccc solid;padding-left:1ex"> Hi group,<br /> <br />
I have a layer with roads which are lines having a style of gray with thin black \
outlines on either side. Another layer (parking lots) has polygons having the same \
color as the roads but not outlined. The parking lot layer is above the road layer \
in rendering order. So road outlines are hidden by the parking lot layer when a \
parking lot intersects a road.<br /> <br />
Here's the trouble - having parking lots with no outline, but roads with \
outlines looks odd. Is there some way to have the outlines of both road and parking \
lot layers removed from rendering when these two features cross?<br /> <br />
One method I've considered is to draw the roads and parking lots as polygons \
in the same layer? It would make drawing the roads non-trivial, but the problem \
with outlines would be eliminated.<br /> <br />
Shane<br />
<br />
_______________________________________________<br />
Qgis-user mailing list<br />
<a href="mailto:Qgis-user@lists.osgeo.org" \
target="_blank">Qgis-user@lists.osgeo.org</a><br /> <a \
href="http://lists.osgeo.org/mailman/listinfo/qgis-user" rel="noreferrer" \
target="_blank">http://lists.osgeo.org/mailman/listinfo/qgis-user</a><br /> \
</blockquote></div><br /><br clear="all" /><div><br /></div>-- <br /><div \
class="gmail_signature"><a href="mailto:tolennon@gmail.com" \
target="_blank">tolennon@gmail.com</a></div> </div>
<p style="margin-top: 2.5em; margin-bottom: 1em; border-bottom: 1px solid \
#000"></p><table style="border: 0"><tbody><tr><th style="text-align: left; \
vertical-align: top;">From:</th><td>Bernd Vogelgesang <bernd.vogelgesang \
gmx.de="gmx.de"></bernd.vogelgesang></td></tr><tr><th style="text-align: left; \
vertical-align: top;">To:</th><td>qgis-user@lists.osgeo.org</td></tr><tr><th \
style="text-align: left; vertical-align: top;">Sent:</th><td>Thu Jul 30 22:50:36 BST \
2015</td></tr><tr><th style="text-align: left; vertical-align: \
top;">Subject:</th><td>Re: [Qgis-user] Layer question</td></tr></tbody></table>
<div>Hi Shane,</div><div>I think without a screenshot, we have no chance to really \
get an idea what it's all about.</div><div>Best to use a service like \
http://imgur.com/ and post the link cause the list will bounce too heavy \
attachments.</div><div><br /></div><div>Bernd</div><div><br /></div><div><br \
/></div><div><br /></div><div>Am 30.07.2015, 23:11 Uhr, schrieb Tom Lennon \
<tolennon@gmail.com>:<br /></div><br /><blockquote style="margin: 0 0 0.80ex; \
border-left: #0000FF 2px solid; padding-left: 1ex"><div dir="ltr"><div \
class="gmail_default" style="font-size:small">Hi Shane:</div><div \
class="gmail_default" style="font-size:small">Have you tried moving the parking lot \
layer to below the road layer?</div><div class="gmail_default" \
style="font-size:small">That way roads over parking lots would always show.</div><div \
class="gmail_default" style="font-size:small"><br /></div><div class="gmail_default" \
style="font-size:small">Tom</div></div><div class="gmail_extra"><br /><div \
class="gmail_quote">On Thu, Jul 30, 2015 at 3:05 PM, Shane <span dir="ltr"><<a \
href="mailto:shaned173@gmail.com" target="_blank">shaned173@gmail.com</a>></span> \
wrote:<br /><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px \
#ccc solid;padding-left:1ex"> Hi group,<br /> <br />
I have a layer with roads which are lines having a style of gray with \
thin black outlines on either side. Another layer (parking lots) has polygons \
having the same color as the roads but not outlined. The parking lot layer is \
above the road layer in rendering order. So road outlines are hidden by the \
parking lot layer when a parking lot intersects a road.<br /> <br />
Here's the trouble - having parking lots with no outline, but roads with \
outlines looks odd. Is there some way to have the outlines of both road and \
parking lot layers removed from rendering when these two features cross?<br /> <br />
One method I've considered is to draw the roads and parking lots as \
polygons in the same layer? It would make drawing the roads non-trivial, but \
the problem with outlines would be eliminated.<br /> <br />
Shane<br />
<br />
_______________________________________________<br />
Qgis-user mailing list<br />
<a href="mailto:Qgis-user@lists.osgeo.org" \
target="_blank">Qgis-user@lists.osgeo.org</a><br /> <a \
href="http://lists.osgeo.org/mailman/listinfo/qgis-user" rel="noreferrer" \
target="_blank">http://lists.osgeo.org/mailman/listinfo/qgis-user</a><br /> \
</blockquote></div><br /><br clear="all" /><div><br /></div>-- <br /><div \
class="gmail_signature"><a href="mailto:tolennon@gmail.com" \
target="_blank">tolennon@gmail.com</a></div> </div>
</blockquote><br /><br /><br /><div id="M2Signature"><div>-- </div><div>Bernd \
Vogelgesang<br />Siedlerstraße 2<br />91083 Baiersdorf/Igelsdorf<br />Tel: \
09133-825374</div></div><p style="margin-top: 2.5em; margin-bottom: 1em; \
border-bottom: 1px solid #000"></p><table style="border: 0"><tbody><tr><th \
style="text-align: left; vertical-align: top;">From:</th><td>Nicolas Cadieux \
<nicolas.cadieux archeotec.ca="archeotec.ca"></nicolas.cadieux></td></tr><tr><th \
style="text-align: left; vertical-align: \
top;">To:</th><td>qgis-user@lists.osgeo.org</td></tr><tr><th style="text-align: left; \
vertical-align: top;">Sent:</th><td>Thu Jul 30 23:07:50 BST 2015</td></tr><tr><th \
style="text-align: left; vertical-align: top;">Subject:</th><td>Re: [Qgis-user] Layer \
question</td></tr></tbody></table><p dir="ltr">Hi,</p> <p dir="ltr">You can play with \
the layer blending. You can use "multiply" , "add", "subtract"... \
(something like that, I am not in front of a computer). There are also the same \
blending options in the vector object styling so that you can select what happens \
when two objects intersect in the same layer.</p> <p dir="ltr">Maybe that could \
help?</p> <p dir="ltr">Nicolas Cadieux M.Sc.<br />
Les Entreprises Archéotec inc. <br />
8548, rue Saint-Denis Montréal H2P 2H2<br />
Téléphone: 514.381.5112  Fax: 514.381.4995<br />
www.archeotec.ca</p>
<div class="gmail_quote">On Jul 30, 2015 5:45 PM, "berndv. [via OSGeo.org]" \
<<a href="/user/SendEmail.jtp?type=node&node=5217890&i=0" target="_top" \
rel="nofollow" link="external">[hidden email]</a>> wrote:<br type="attribution" \
/><blockquote style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex" \
class="quote">
<div>Hi Shane,</div><div>I think without a screenshot, we have no chance to really \
get an idea what it's all about.</div><div>Best to use a service like \
http://imgur.com/ and post the link cause the list will bounce too heavy \
attachments.</div><div><br /></div><div>Bernd</div><div><br /></div><div><br \
/></div><div><br /></div><div>Am 30.07.2015, 23:11 Uhr, schrieb Tom Lennon <<a \
href="/user/SendEmail.jtp?type&#61;node&amp;node&#61;5217887&amp;i&#61;0">[hidden \
email]>:<br /></div><br /><div dir="ltr"><div style="font-size:small">Hi \
Shane:</div><div style="font-size:small">Have you tried moving the parking lot layer \
to below the road layer?</div><div style="font-size:small">That way roads over \
parking lots would always show.</div><div style="font-size:small"><br /></div><div \
style="font-size:small">Tom</div></div><div><br /><div class="elided-text">On Thu, \
Jul 30, 2015 at 3:05 PM, Shane <span dir="ltr"><<a \
href="/user/SendEmail.jtp?type&#61;node&amp;node&#61;5217887&amp;i&#61;1">[hidden \
email]></span> wrote:<br /> Hi group,<br /> <br />
I have a layer with roads which are lines having a style of gray with thin black \
outlines on either side. Another layer (parking lots) has polygons having the same \
color as the roads but not outlined. The parking lot layer is above the road layer \
in rendering order. So road outlines are hidden by the parking lot layer when a \
parking lot intersects a road.<br /> <br />
Here's the trouble - having parking lots with no outline, but roads with \
outlines looks odd. Is there some way to have the outlines of both road and parking \
lot layers removed from rendering when these two features cross?<br /> <br />
One method I've considered is to draw the roads and parking lots as polygons \
in the same layer? It would make drawing the roads non-trivial, but the problem \
with outlines would be eliminated.<br /> <br />
Shane<br />
<br />
_______________________________________________<br />
Qgis-user mailing list<br />
<a href="/user/SendEmail.jtp?type&#61;node&amp;node&#61;5217887&amp;i&#61;2">[hidden \
email]<br /> <a href="http://lists.osgeo.org/mailman/listinfo/qgis-user" \
target="_top" rel="nofollow" \
link="external">http://lists.osgeo.org/mailman/listinfo/qgis-user</a><br /> \
</div></div></blockquote></div><br /><br clear="all" /><div><br /></div>-- <br \
/><div><a href="/user/SendEmail.jtp?type&#61;node&amp;node&#61;5217887&amp;i&#61;3">[hidden \
email]</div>
<br /><br /><br /><div><div>-- </div><div>Bernd Vogelgesang<br />Siedlerstraße 2<br \
/>91083 Baiersdorf/Igelsdorf<br />Tel: 09133-825374</div></div><br \
/>_______________________________________________ <br />Qgis-user mailing list
<br /><a href="/user/SendEmail.jtp?type&#61;node&amp;node&#61;5217887&amp;i&#61;4">[hidden \
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target="_top" rel="nofollow" \
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View this message in context: <a \
href="http://osgeo-org.1560.x6.nabble.com/Layer-question-tp5217849p5217890.html">Re: \
Layer question</a><br /> Sent from the <a \
href="http://osgeo-org.1560.x6.nabble.com/Quantum-GIS-User-f4125267.html">Quantum GIS \
- User mailing list archive</a> at Nabble.com.<br /><p style="margin-top: 2.5em; \
margin-bottom: 1em; border-bottom: 1px solid #000"></p><table style="border: \
0"><tbody><tr><th style="text-align: left; vertical-align: top;">From:</th><td>Nick \
Papadonis <npapadonis gmail.com="gmail.com"></npapadonis></td></tr><tr><th \
style="text-align: left; vertical-align: top;">To:</th><td>"Håvard Tveite" \
<havard.tveite nmbu.no="nmbu.no"></havard.tveite></td></tr><tr><th style="text-align: \
left; vertical-align: top;">Cc:</th><td>qgis-user@lists.osgeo.org</td></tr><tr><th \
style="text-align: left; vertical-align: top;">Sent:</th><td>Fri Jul 31 00:45:56 BST \
2015</td></tr><tr><th style="text-align: left; vertical-align: \
top;">Subject:</th><td>Re: [Qgis-user] How to convert raster routes into vector \
format?</td></tr></tbody></table><pre class="k9mail">Hi Havard,<br /><br \
/>Unfortunately, the expression below results in a complete black TIFF. I am \
referencing the correct layer. Any ideas?<br /><br />Thanks<br />Nick<br /><br \
/><blockquote class="gmail_quote" style="margin: 0pt 0pt 1ex 0.8ex; border-left: 1px \
solid #729fcf; padding-left: 1ex;"> On Jul 29, 2015, at 4:34 PM, Håvard Tveite \
<havard.tveite@nmbu.no> wrote:<br /> <br /> With QGIS 2.10, the following \
should work (probably also OK<br /> for earlier versions).<br /> <br /> Check the \
band values of your colour using the info button,<br /> and use the values in the \
expression below (assuming the<br /> name of your raster layer is yourraster) instead \
of 116, 20<br /> and 31:<br /> <br /> ("yourraster@1" = 116 AND "yourraster@2" = 20 \
AND "yourraster@3" = 31) * 1<br /> <br /> This should give you a binary raster with 1 \
in the pixels<br /> that have your colour and 0 in the pixels with other colours.<br \
/> <br /> In the style dialogue you can use the following to see the<br /> resulting \
binary image:<br /> Colour gradient: "white to black"<br /> Min: 0<br /> Max: 1<br /> \
<br /> You should be able to use r.thin on that image, but I am not<br /> able to \
test this now, as I am on Ubuntu, and have not been<br /> able to get GRASS to work \
through Processing on that platform<br /> for QGIS 2.10.<br /> <br /> Håvard<br /> \
<br /> On 29. juli 2015 16:40, Nick Papadonis wrote:<br /><blockquote \
class="gmail_quote" style="margin: 0pt 0pt 1ex 0.8ex; border-left: 1px solid #ad7fa8; \
padding-left: 1ex;"> Hi Håvard,<br /> <br /> I found the raster calculator and read \
the online manual for it, however am still a bit lost. I was also playing with the \
Style properties and color bands last night to try to accomplish this. I was unable \
to get a single binary image with the single color (red in this case). I think the \
understand the r.thin suggestion and that it will thin the single color thick lines \
for vectorization. Appreciate if you can expand on obtaining a binary skeleton of \
the one color of the trails.<br /> <br /> Thanks again,<br /> Nick<br /> <br \
/><blockquote class="gmail_quote" style="margin: 0pt 0pt 1ex 0.8ex; border-left: 1px \
solid #8ae234; padding-left: 1ex;"> On Jul 29, 2015, at 7:18 AM, Havard Tveite \
<havard.tveite@nmbu.no> wrote:<br /> <br /> If you are going to use GRASS <a \
href="http://r.to">r.to</a>.vect (for instance through QGIS<br /> Processing), you \
will need a binary skeleton image.<br /> You could get one by using the raster \
calculator to extract<br /> your single colour as a binary image, and then GRASS \
r.thin<br /> (available in QGIS Processing) to get the skeleton.<br /> <br /> \
Håvard<br /> <br /> On 29/7/2015 8:36:AM, Nick Papadonis wrote:<br /><blockquote \
class="gmail_quote" style="margin: 0pt 0pt 1ex 0.8ex; border-left: 1px solid #fcaf3e; \
padding-left: 1ex;"> Hi Folks,<br /> <br /> I have a map with numerous trails in a \
single color and would like to vectorize these. Is there a mode Qgis can be placed \
in such that a color can be selected for inclusion in the vectorization process? \
I.e. to make converting these routes to vector format easier?<br /> <br /> Thanks \
again<br /><hr /><br /> Qgis-user mailing list<br /> Qgis-user@lists.osgeo.org<br /> \
<a href="http://lists.osgeo.org/mailman/listinfo/qgis-user">http://lists.osgeo.org/mailman/listinfo/qgis-user</a><br \
/> <br /></blockquote></blockquote> <br /></blockquote></blockquote><br /><br \
/></pre><p style="margin-top: 2.5em; margin-bottom: 1em; border-bottom: 1px solid \
#000"></p><table style="border: 0"><tbody><tr><th style="text-align: left; \
vertical-align: top;">From:</th><td>Nick Papadonis <npapadonis \
gmail.com="gmail.com"></npapadonis></td></tr><tr><th style="text-align: left; \
vertical-align: top;">To:</th><td>Qgis-user@lists.osgeo.org</td></tr><tr><th \
style="text-align: left; vertical-align: top;">Sent:</th><td>Fri Jul 31 02:07:44 BST \
2015</td></tr><tr><th style="text-align: left; vertical-align: \
top;">Subject:</th><td>[Qgis-user] Raster Calculator Expression to determine \
color</td></tr></tbody></table><pre class="k9mail">HI Folks,<br /><br />I'm trying to \
use the following expression to pick up the red colored routes on a map in which I \
used the info pointer tool to get the band values for the color. <br /><br />("m@1" \
< 238 AND "m@1" > 213 AND "m@2" < 123 AND "m@2" > 98 AND "m@3" < 125 \
AND "m@3" < 99) * 1<br /><br />Unfortunately, when this expression is used the \
resulting map is black with no other pixels for the detected color.<br /><br />If I \
break down this expression to a simple "greater than" line for single band, then \
things work.<br /><br />Does anyone know where this expression needs to be \
corrected?<br /><br />Thanks again,<br />Nick<br /></pre><p style="margin-top: 2.5em; \
margin-bottom: 1em; border-bottom: 1px solid #000"></p><table style="border: \
0"><tbody><tr><th style="text-align: left; vertical-align: top;">From:</th><td>Nyall \
Dawson <nyall.dawson gmail.com="gmail.com"></nyall.dawson></td></tr><tr><th \
style="text-align: left; vertical-align: top;">To:</th><td>Nick Papadonis <npapadonis \
gmail.com="gmail.com"></npapadonis></td></tr><tr><th style="text-align: left; \
vertical-align: top;">Cc:</th><td>Qgis-user@lists.osgeo.org</td></tr><tr><th \
style="text-align: left; vertical-align: top;">Sent:</th><td>Fri Jul 31 02:29:34 BST \
2015</td></tr><tr><th style="text-align: left; vertical-align: \
top;">Subject:</th><td>Re: [Qgis-user] Raster Calculator Expression to determine \
color</td></tr></tbody></table><p dir="ltr"><br /> On 31 Jul 2015 11:07 am, \
"Nick Papadonis" <<a \
href="mailto:npapadonis@gmail.com">npapadonis@gmail.com</a>> wrote:<br /> ><br \
/> > HI Folks,<br />
><br />
> I'm trying to use the following expression to pick up the red colored routes on \
a map in which I used the info pointer tool to get the band values for the color.<br \
/> ><br />
> ("m@1" < 238 AND "m@1" > 213 AND "m@2" < 123 AND \
"m@2" > 98 AND "m@3" < 125 AND "m@3" < 99) * 1</p> <p \
dir="ltr">Should that last check be "m@3" > 99?</p> <p \
dir="ltr">Nyall</p> <p dir="ltr">><br />
> Unfortunately, when this expression is used the resulting map is black with no \
other pixels for the detected color.<br /> ><br />
> If I break down this expression to a simple "greater than" line for single band, \
then things work.<br /> ><br />
> Does anyone know where this expression needs to be corrected?<br />
><br />
> Thanks again,<br />
> Nick<br />
> _______________________________________________<br />
> Qgis-user mailing list<br />
> <a href="mailto:Qgis-user@lists.osgeo.org">Qgis-user@lists.osgeo.org</a><br />
> <a href="http://lists.osgeo.org/mailman/listinfo/qgis-user">http://lists.osgeo.org/mailman/listinfo/qgis-user</a></p>
<p style="margin-top: 2.5em; margin-bottom: 1em; border-bottom: 1px solid \
#000"></p><table style="border: 0"><tbody><tr><th style="text-align: left; \
vertical-align: top;">From:</th><td>Nick Papadonis <npapadonis \
gmail.com="gmail.com"></npapadonis></td></tr><tr><th style="text-align: left; \
vertical-align: top;">To:</th><td>Nyall Dawson <nyall.dawson \
gmail.com="gmail.com"></nyall.dawson></td></tr><tr><th style="text-align: left; \
vertical-align: top;">Cc:</th><td>Qgis-user@lists.osgeo.org</td></tr><tr><th \
style="text-align: left; vertical-align: top;">Sent:</th><td>Fri Jul 31 02:30:44 BST \
2015</td></tr><tr><th style="text-align: left; vertical-align: \
top;">Subject:</th><td>Re: [Qgis-user] Raster Calculator Expression to determine \
color</td></tr></tbody></table><br class="" /><div><blockquote type="cite" \
class=""><div class="">On Jul 30, 2015, at 9:29 PM, Nyall Dawson <<a \
href="mailto:nyall.dawson@gmail.com" class="">nyall.dawson@gmail.com</a>> \
wrote:</div><br class="Apple-interchange-newline" /><div class=""><p dir="ltr" \
class=""><br class="" /> On 31 Jul 2015 11:07 am, "Nick Papadonis" <<a \
href="mailto:npapadonis@gmail.com" class="">npapadonis@gmail.com</a>> wrote:<br \
class="" /> ><br class="" />
> HI Folks,<br class="" />
><br class="" />
> I'm trying to use the following expression to pick up the red colored routes on \
a map in which I used the info pointer tool to get the band values for the color.<br \
class="" /> ><br class="" />
> ("m@1" < 238 AND "m@1" > 213 AND "m@2" < 123 AND "m@2" > 98 AND \
"m@3" < 125 AND "m@3" < 99) * 1</p><p dir="ltr" class="">Should that last check \
be "m@3" > 99?</p><div class=""><br class="" /></div></div></blockquote>Yeah, I \
changed that and still same results. If I specify on > and remove the < \
expressions, then everything works. Very odd considering the color is within \
the range above (with the line you referenced fixed).</div><div><br class="" \
/></div><div>Thanks<br class="" /><blockquote type="cite" class=""><div class=""><p \
dir="ltr" class="">Nyall</p><p dir="ltr" class="">><br class="" /> > \
Unfortunately, when this expression is used the resulting map is black with no other \
pixels for the detected color.<br class="" /> ><br class="" />
> If I break down this expression to a simple "greater than" line for single band, \
then things work.<br class="" /> ><br class="" />
> Does anyone know where this expression needs to be corrected?<br class="" />
><br class="" />
> Thanks again,<br class="" />
> Nick<br class="" />
> _______________________________________________<br class="" />
> Qgis-user mailing list<br class="" />
> <a href="mailto:Qgis-user@lists.osgeo.org" \
class="">Qgis-user@lists.osgeo.org</a><br class="" /> > <a \
href="http://lists.osgeo.org/mailman/listinfo/qgis-user" \
class="">http://lists.osgeo.org/mailman/listinfo/qgis-user</a></p> \
</div></blockquote></div><br class="" /><p style="margin-top: 2.5em; margin-bottom: \
1em; border-bottom: 1px solid #000"></p><table style="border: 0"><tbody><tr><th \
style="text-align: left; vertical-align: top;">From:</th><td>Nick Papadonis \
<npapadonis gmail.com="gmail.com"></npapadonis></td></tr><tr><th style="text-align: \
left; vertical-align: top;">To:</th><td>Nyall Dawson <nyall.dawson \
gmail.com="gmail.com">, Qgis-user@lists.osgeo.org</nyall.dawson></td></tr><tr><th \
style="text-align: left; vertical-align: top;">Sent:</th><td>Fri Jul 31 02:56:24 BST \
2015</td></tr><tr><th style="text-align: left; vertical-align: \
top;">Subject:</th><td>Re: [Qgis-user] Raster Calculator Expression to determine \
color</td></tr></tbody></table><br class="" /><div><blockquote type="cite" \
class=""><div class="">On Jul 30, 2015, at 9:29 PM, Nyall Dawson <<a \
href="mailto:nyall.dawson@gmail.com" class="">nyall.dawson@gmail.com</a>> \
wrote:</div><div class=""><p dir="ltr" class="">On 31 Jul 2015 11:07 am, "Nick \
Papadonis" <<a href="mailto:npapadonis@gmail.com" \
class="">npapadonis@gmail.com</a>> wrote:<br class="" /> ><br class="" />
> HI Folks,<br class="" />
><br class="" />
> I'm trying to use the following expression to pick up the red colored routes on \
a map in which I used the info pointer tool to get the band values for the color.<br \
class="" /> ><br class="" />
> ("m@1" < 238 AND "m@1" > 213 AND "m@2" < 123 AND "m@2" > 98 AND \
"m@3" < 125 AND "m@3" < 99) * 1</p><p dir="ltr" class="">Should that last check \
be "m@3" > 99?</p><div class=""><br class="" /></div></div></blockquote><div><br \
class="" /></div><div>I corrected above to:</div><div>("m@1" < 238 AND "m@1" > \
213 AND "m@2" < 123 AND "m@2" > 98 AND "m@3" < 125 AND "m@3" > 99) * \
1</div><div><br class="" /></div><div>with the same results which is black output \
tiff.</div><div><br class="" /></div><div>I then tried individual expressions for \
each band as separate steps (sanity check):</div><div>("m@1" < 238 AND "m@1" > \
213) * 1</div><div>("m@2" < 123 AND "m@2" > 98) * 1</div><div>("m@3" < 125 \
AND "m@3" > 99) * 1</div><div><br class="" /></div><div>These all produce a masked \
image, however masked incorrectly because I'm evaluating only a single band in the \
Raster Calculator.</div><div><br class="" /></div><div>When I combine evaluation of \
bands as above or below to pick pixels in color range:</div><div><br class="" \
/></div> (("m@1" < 238 AND "m@1" > 210) AND ("m@2" < 123 AND "m@2" > \
94) AND ("m@3" < 130 AND "m@3" > 98)) * 1</div><div><br class="" /></div><div>I \
get a black image with no matches. I expected at least one pixel identified \
using this expression because I evaluate a pixel at 224, 108, 115 and there are many \
other pixels in above range.</div><div><br class="" /></div><div>Does anyone know if \
my expression needs correction or the Raster Calculator can only evaluate a single \
band in the expression?</div><div><br class="" /></div><div>Thanks \
again,</div><div>Nick</div><div><br class="" /><blockquote type="cite" class=""><div \
class=""><p dir="ltr" class="">Nyall</p><p dir="ltr" class="">><br class="" /> \
> Unfortunately, when this expression is used the resulting map is black with no \
other pixels for the detected color.<br class="" /> ><br class="" />
> If I break down this expression to a simple "greater than" line for single band, \
then things work.<br class="" /> ><br class="" />
> Does anyone know where this expression needs to be corrected?<br class="" />
><br class="" />
> Thanks again,<br class="" />
> Nick<br class="" />
> _______________________________________________<br class="" />
> Qgis-user mailing list<br class="" />
> <a href="mailto:Qgis-user@lists.osgeo.org" \
class="">Qgis-user@lists.osgeo.org</a><br class="" /> > <a \
href="http://lists.osgeo.org/mailman/listinfo/qgis-user" \
class="">http://lists.osgeo.org/mailman/listinfo/qgis-user</a></p> \
</div></blockquote></div><br class="" /><p style="margin-top: 2.5em; margin-bottom: \
1em; border-bottom: 1px solid #000"></p><table style="border: 0"><tbody><tr><th \
style="text-align: left; vertical-align: top;">From:</th><td>Nick Papadonis \
<npapadonis gmail.com="gmail.com"></npapadonis></td></tr><tr><th style="text-align: \
left; vertical-align: top;">To:</th><td>Qgis-user@lists.osgeo.org</td></tr><tr><th \
style="text-align: left; vertical-align: top;">Sent:</th><td>Fri Jul 31 05:39:12 BST \
2015</td></tr><tr><th style="text-align: left; vertical-align: \
top;">Subject:</th><td>Re: [Qgis-user] Raster Calculator \
bug?</td></tr></tbody></table><pre class="k9mail">Folks,<br /><br />I'm using QGIS \
10.1. The following expressions result in a black raster of 0's, when I expected \
only red pixels to appears in the binary image indicating routes on a map:<br /><br \
/>a) ("m@1" < 238 AND "m@1" > 213 AND "m@2" < 123 AND "m@2" > 98 AND \
"m@3" < 125 AND "m@3" > 99) * 1<br />b) (("m@1" < 238 AND "m@1" > 210) * \
1) * (("m@2" < 123 AND "m@2" > 94) * 1) * (("m@3" < 130 AND "m@3" > 98) * \
1)<br /><br />I then tried the following individual expressions for each band as \
separate steps (sanity check) and they work to cover the pixels in range:<br />c) \
("m@1" < 238 AND "m@1" > 213) * 1<br />d) ("m@2" < 123 AND "m@2" > 98) * \
1<br />e) ("m@3" < 125 AND "m@3" > 99) * 1<br /><br />I then tried the \
following expression which appears to create a proper greyscale image focusing on the \
red pixels. I replaced the multiplication with addition to see what was \
happening:<br />f) (("m@1" < 238 AND "m@1" > 210) * 1) + (("m@2" < 123 AND \
"m@2" > 94) * 1) + (("m@3" < 130 AND "m@3" > 98) * 1)<br /><br />The \
resulting raster has a Min = 0 and Max = 1.998. I was expecting it to be Min = 0 and \
Max = 3. The value of 3 would indicate all 3 bands were positive on color match. I \
then go to the layer properties and load calculate min/max again and it is Min = 0 \
and Max = 3. I tried to change the min/max settings on they layer and these settings \
will not stay set. The layer goes back to Max = 1.998. What's even more odd is the \
max being a floating point number. I suspect that may be part of the issue. Anyone \
know why this is the case for integer band values? Has anyone successfully used the \
Raster Calculator to perform this sort of work before?<br /><br />Thanks again,<br \
/>Nick<br /></pre><p style="margin-top: 2.5em; margin-bottom: 1em; border-bottom: 1px \
solid #000"></p><pre class="k9mail"><hr /><br />Qgis-user mailing list<br \
/>Qgis-user@lists.osgeo.org<br /><a \
href="http://lists.osgeo.org/mailman/listinfo/qgis-user">http://lists.osgeo.org/mailman/listinfo/qgis-user</a></pre></blockquote></div><br>
--<br>
Jonathan Webb <br>
Freelance GIS specialist<br>
07941 921905<br>
<a href="http://www.jwebbgis.co.uk">www.jwebbgis.co.uk</a><br>
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