add image-from-codec to c api

gm/cgm.c

Index: gm/cgm.c
diff --git a/gm/cgm.c b/gm/cgm.c
index cddb2c14e28e755413683d3429770d3a5b524586..5a20a7d1bfe3a8c3e8def08e217ef495e015cecd 100644
--- a/gm/cgm.c
+++ b/gm/cgm.c
@@ -9,6 +9,8 @@
 // DO NOT USE -- FOR INTERNAL TESTING ONLY
 
 #include "sk_canvas.h"
+#include "sk_data.h"
+#include "sk_image.h"
 #include "sk_paint.h"
 #include "sk_shader.h"
 #include "sk_surface.h"
@@ -24,25 +26,49 @@ static sk_shader_t* make_shader() {
     return sk_shader_new_linear_gradient(pts, colors, NULL, 2, CLAMP_SK_SHADER_TILEMODE, NULL);
 }
 
-void sk_test_c_api(sk_canvas_t* canvas) {
+static void do_draw(sk_canvas_t* canvas) {
     sk_paint_t* paint = sk_paint_new();
     sk_paint_set_antialias(paint, true);
-
+    
     sk_paint_set_color(paint, 0xFFFFFFFF);
     sk_canvas_draw_paint(canvas, paint);
-
+    
     sk_rect_t r = { 10, 10, W - 10, H - 10 };
-
+    
     sk_paint_set_color(paint, 0xFFFF0000);
     sk_canvas_draw_rect(canvas, &r, paint);
-
+    
     sk_shader_t* shader = make_shader();
     sk_paint_set_shader(paint, shader);
     sk_shader_unref(shader);
-
+    
     sk_canvas_draw_oval(canvas, &r, paint);
-
+    
     sk_paint_delete(paint);
 }
 
+void sk_test_c_api(sk_canvas_t* canvas) {
+    do_draw(canvas);
+
+    sk_imageinfo_t info = {
+        W, H, sk_colortype_get_default_8888(), OPAQUE_SK_ALPHATYPE
+    };
+    sk_surface_t* surf = sk_surface_new_raster(&info);
+    do_draw(sk_surface_get_canvas(surf));
+
+    sk_image_t* img0 = sk_surface_new_image_snapshot(surf);
+    sk_surface_unref(surf);
+
+    sk_canvas_draw_image(canvas, img0, W + 10, 10, NULL);
+
+    sk_data_t* data = sk_image_encode(img0);
+    sk_image_unref(img0);
+
+    sk_image_t* img1 = sk_image_new_from_data(data);
+    sk_data_unref(data);
+
+    sk_canvas_draw_image(canvas, img1, W/2, H/2, NULL);
+    sk_image_unref(img1);
+}
+