[cairo] Need help using recording surface

[cecashon at aol.com]

Hi David,

There are some cairo_show_page() functions that you don't need. Going from pixels to points for the PDF can be a challenge. See if the following is of any help getting it to work.

Eric

//gcc -Wall -g copy_surface2.c -o copy_surface2 `pkg-config --cflags --libs cairo`

//Tested on Ubuntu18.04.

#include<cairo.h>
#include<cairo-pdf.h>
#include<stdio.h>

//Width and height of drawings.
static double width=400.0;
static double height=400.0;
//PDF's are in points so adjust the drawing if you want it the same size as the .png
//on screen. Try different values here.
static double ppi=100.0;

int main()
  {
    //Create a recording surface.
    cairo_rectangle_t extents={.x=0.0, .y=0.0, .width=width, .height=height};
    cairo_surface_t  *surface1=cairo_recording_surface_create(CAIRO_CONTENT_COLOR_ALPHA, &extents);
    cairo_t *cr1=cairo_create(surface1);
    //Paint the background white.
    cairo_set_source_rgba(cr1, 1.0, 1.0, 1.0, 1.0);
    cairo_paint(cr1);
    //Draw an x or other drawing in the recording surface.
    cairo_set_line_width(cr1, 10.0);
    cairo_set_source_rgba(cr1, 0.0, 1.0, 0.0, 1.0); 
    cairo_move_to(cr1, 0.0, 0.0);
    cairo_line_to(cr1, 200.0, 200.0);
    cairo_stroke(cr1);
    cairo_move_to(cr1, 0.0, 200.0);
    cairo_line_to(cr1, 200.0, 0.0);
    cairo_stroke(cr1); 
  
    //Save the recording surface to a .png and .pdf.
    printf("Save a_test.png\n");
    cairo_surface_t *surface2=cairo_image_surface_create(CAIRO_FORMAT_ARGB32, width, height);
    cairo_t *cr2=cairo_create(surface2);
    cairo_set_source_surface(cr2, surface1, 0.0, 0.0);
    cairo_paint(cr2); 
    cairo_surface_write_to_png(surface2, "a_test.png");

    printf("Save a_test.pdf\n");
    double points_scale=72.0/ppi;
    cairo_surface_t *surface3=cairo_pdf_surface_create("a_test.pdf", width*points_scale, height*points_scale);
    cairo_t *cr3=cairo_create(surface3);
    cairo_scale(cr3, points_scale, points_scale);
    cairo_set_source_surface(cr3, surface1, 0.0, 0.0);
    cairo_paint(cr3);  

    //Clean up.
    cairo_destroy(cr1);
    cairo_destroy(cr2);
    cairo_destroy(cr3);
    cairo_surface_destroy(surface1);
    cairo_surface_destroy(surface2);
    cairo_surface_destroy(surface3);

    //For testing with valgrind.
    cairo_debug_reset_static_data();
  
    return 0;
  }
   
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