[prev in list] [next in list] [prev in thread] [next in thread] 

List:       cairo
Subject:    [cairo] Question regarding recording surfaces
From:       Zoltán Turányi <teknos () gmail ! com>
Date:       2011-02-25 16:26:09
Message-ID: AANLkTikGD82X1DDbsJs_Dw5_6qnjN6yNRkyJ-KKCshXa () mail ! gmail ! com
[Download RAW message or body]

[Attachment #2 (multipart/alternative)]


Hi,

I plan to use recording surfaces to create a drawing and then replay it into
a window using different scaling factors (as the user zooms in). I read the
documentation and it seems to say that recording surfaces record the
high-level drawing commands - from which I would expect a high resolution
output if replayed on a high resolution target surface (appropriate scaling
applied to the context onto which it is being replayed).

I do not seem to be able to get this behaviour. In the below code I draw
some text and I replay it onto a PNG surface with 2x magnification. Yet the
text and line comes out as blurred - as if it were already rendered to some
bitmap on the recording surface (instead of just being recorded as a
show_text and a stroke). (See attachment.)

Is this something fundamental or am I doing something wrong?

As an additional comment: if I create the recording surface with no extents
given (NULL), the text and line does not replay onto the target surface at
all. Any hints on why?

Thanks in advance,
Zoltan

[Attachment #5 (text/html)]

<div>Hi,</div><div>=C2=A0</div><div>I plan to use recording surfaces to cre=
ate a drawing and then replay it into a window using different scaling fact=
ors (as the user zooms in). I read the documentation and it seems to say th=
at recording surfaces record the high-level drawing commands - from which I=
 would expect a high resolution output if replayed on a high resolution tar=
get surface (appropriate scaling applied to the context onto which it is be=
ing replayed).</div>
<div>=C2=A0</div><div>I do not seem to be able to get this behaviour. In th=
e below code I draw some text and I replay it onto a PNG surface with 2x ma=
gnification. Yet the text and line comes out as blurred - as if it were alr=
eady rendered to some bitmap on the recording surface (instead of just bein=
g recorded as a show_text and a stroke). (See attachment.)</div>
<div>=C2=A0</div><div>Is this something fundamental or am I doing something=
 wrong?</div><div>=C2=A0</div><div>As an additional comment: if I create th=
e recording surface with no extents given (NULL), the text and line does no=
t replay onto the target surface at all. Any hints on why?</div>
<div>=C2=A0</div><div>Thanks in advance,</div><div>Zoltan</div><div>=C2=A0<=
/div>

--0015174479eaa2ac94049d1dc9f9--
["result.png" (image/png)]
["test.c" (text/x-csrc)]

#include "cairo.h"
#include "stdio.h"

cairo_status_t write_func(void * closure, const unsigned char *data, unsigned length)
{
    if (closure==NULL) return CAIRO_STATUS_SUCCESS;
    if (length == fwrite(data, 1, length, (FILE*)closure))
        return CAIRO_STATUS_SUCCESS;
    else
        return CAIRO_STATUS_WRITE_ERROR;
}



int main()
{
    //Create recorded surface with text
    cairo_rectangle_t ext = {0, 0, 100, 100};
    cairo_surface_t *recording = cairo_recording_surface_create(CAIRO_CONTENT_COLOR_ALPHA, &ext);
    cairo_t *cr = cairo_create(recording);
    cairo_move_to(cr, 10, 20);
    cairo_set_source_rgb(cr, 0, 0, 0);
    cairo_show_text(cr, "Text - Recorded");
    cairo_stroke(cr);
    cairo_destroy(cr);

    //Create target surface
    cairo_surface_t *target = cairo_image_surface_create (CAIRO_FORMAT_RGB24, 200, 200);
    cr = cairo_create(target);
    cairo_set_source_rgb(cr, 1, 1, 1);
    cairo_rectangle(cr, 0, 0, 200, 200);
    cairo_fill(cr);
    //Scale x2
    cairo_scale(cr, 2, 2);

    //Replay recorded surface
    cairo_set_source_surface (cr, recording, 0.0, 0.0);
    cairo_paint (cr);

    //Draw text for comparison
    cairo_move_to(cr, 10, 40);
    cairo_set_source_rgb(cr, 0, 0, 0);
    cairo_show_text(cr, "Text - Direct");
    cairo_stroke(cr);

    //Clean up, write file
    cairo_destroy (cr);
    FILE *file = fopen("result.png", "wb");
    cairo_surface_write_to_png_stream (target, write_func, file);
    cairo_surface_destroy(target);
    fclose(file);
}


--
cairo mailing list
cairo@cairographics.org
http://lists.cairographics.org/mailman/listinfo/cairo

[prev in list] [next in list] [prev in thread] [next in thread]