Cairo demo

cairo_demo.c

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

// sudo apt-get install libpango1.0-dev
// gcc cairo-demo.c $(pkg-config --cflags --libs pangocairo)
int main()
{
        cairo_surface_t *surface = cairo_image_surface_create(CAIRO_FORMAT_ARGB32, 200, 200);
        cairo_t *cr = cairo_create(surface);
        cairo_surface_destroy(surface);

        /* Fill everything with white */
        cairo_set_source_rgb(cr, 1, 1, 1);
        cairo_paint(cr);

        /* Draw some text */
        cairo_select_font_face(cr, "monospace", CAIRO_FONT_SLANT_NORMAL, CAIRO_FONT_WEIGHT_NORMAL);
        cairo_set_font_size(cr, 32);
        cairo_set_source_rgb(cr, 0, 0, 0);
        cairo_move_to(cr, 0, 23);
        cairo_show_text(cr, "ABC");

        cairo_glyph_t glyph;
        cairo_show_glyphs (cr, &glyph, 1);

	cairo_text_extents_t extents;
	cairo_text_extents(cr, "A", &extents);
        printf("x_bearing:%f, y_bearing:%f\n", extents.x_bearing, extents.y_bearing);
        printf("width:%f, height:%f\n", extents.width, extents.height);
        printf("x_advance:%f, y_advance:%f\n", extents.x_advance, extents.y_advance);


        cairo_surface_write_to_png(cairo_get_target(cr), "out.png");
        cairo_destroy(cr);
        return 0;
}

cairo_demo2.c

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

int main()
{
        cairo_surface_t *surface = cairo_image_surface_create_from_png("/home/qichunren/code/pis/ntpis-broadcast/misc/test.png");
        cairo_t *cr = cairo_create(surface);
        unsigned char * data_buff = cairo_image_surface_get_data(surface);
        int width = cairo_image_surface_get_width(surface);
        int height = cairo_image_surface_get_height(surface);
        int stride = cairo_image_surface_get_stride(surface);
        int data_size = stride * height;
	printf("width/height: %d/%d,stride:%d, data_size: %d\n", width, height, stride, data_size);	
	for(int i = 0; i < data_size;i++)
	{
            if(i%4 ==0)
            {
	        printf("\n");            
                printf("%d: %02X ", i, data_buff[i]);
                }
	    else
            {
                printf("%02X ", data_buff[i]);
            }
            

	}
        printf("\n");

        cairo_surface_destroy(surface);
       


        // cairo_surface_write_to_png(cairo_get_target(cr), "out.png");
        cairo_destroy(cr);
        return 0;
}

cairo_demo3.c

#include <math.h>
#include <pango/pangocairo.h>

#define FONT "Sans Bold 27"

// sudo apt-get install libpango1.0-dev
// gcc cairo-demo.c $(pkg-config --cflags --libs pangocairo) -lm

static cairo_t*
create_layout_context ()
{
    cairo_surface_t *temp_surface;
    cairo_t *context;

    temp_surface = cairo_image_surface_create (CAIRO_FORMAT_ARGB32, 0, 0);
    context = cairo_create (temp_surface);
    cairo_surface_destroy (temp_surface);

    return context;
}

static void
get_text_size (PangoLayout *layout,
                unsigned int *width,
                unsigned int *height)
{
    pango_layout_get_pixel_size(layout, width, height);
}

static void
draw_text (cairo_t *cr, const char * text, int width, int height)
{

  PangoLayout *layout;
  PangoFontDescription *desc;

  /* Create a PangoLayout, set the font and text */
  layout = pango_cairo_create_layout (cr);

  pango_layout_set_text (layout, text, -1);
  desc = pango_font_description_from_string (FONT);
  pango_layout_set_font_description(layout, desc);
  pango_font_description_free (desc);

  /* Draw the layout N_WORDS times in a circle */

      cairo_save (cr);

      /* Gradient from red at angle == 60 to blue at angle == 240 */

      cairo_set_source_rgb (cr, 0, 0, 0);

      /* Inform Pango to re-layout the text with the new transformation */
      pango_cairo_update_layout (cr, layout);

      // pango_layout_get_size (layout, &width, &height);
      cairo_move_to (cr, 0, 0);
      pango_cairo_show_layout (cr, layout);

      cairo_restore (cr);

  /* free the layout object */
  g_object_unref (layout);
}

int main (int argc, char **argv)
{
    const char * display_text = "临时停车";
  cairo_t *cr;
  cairo_t *temp_cr;
  char *filename;
  cairo_status_t status;
  cairo_surface_t *surface;
  cairo_surface_t *temp_surface;

    filename = "/home/qichunren/code/pis/ntpis-broadcast/misc/aaa.png";

    PangoLayout *layout;
    temp_surface = cairo_image_surface_create(CAIRO_FORMAT_ARGB32, 0, 0);
    temp_cr = cairo_create(temp_surface);
    cairo_surface_destroy(temp_surface);

    /* Create a PangoLayout, set the font and text */
    layout = pango_cairo_create_layout(temp_cr);
    pango_layout_set_text(layout, display_text, -1);
    PangoFontDescription * desc = pango_font_description_from_string(FONT);
    pango_layout_set_font_description(layout, desc);
    pango_font_description_free(desc);

    unsigned int text_width;
    unsigned int text_height;
    pango_layout_get_pixel_size(layout, &text_width, &text_height);
    cairo_destroy(temp_cr);

    surface = cairo_image_surface_create(CAIRO_FORMAT_ARGB32, text_width, text_height);
    cr = cairo_create(surface);

    cairo_set_source_rgb(cr, 1.0, 1.0, 1.0);
    cairo_paint(cr);
    draw_text(cr, display_text, text_width, text_height);
    cairo_destroy(cr);

  status = cairo_surface_write_to_png(surface, filename);
  cairo_surface_destroy (surface);

  if (status != CAIRO_STATUS_SUCCESS)
    {
      g_printerr ("Could not save png to '%s'\n", filename);
      return 1;
    }

  return 0;
}