fix: drawImage canvas implementation (#989)

__test__/regression.spec.ts

@@ -266,3 +266,24 @@ test('putImageData double free', (t) => {
     ctx.putImageData(imgData, 0, 0, 0, 0, canvas.width, canvas.height)
   })
 })
+
+// https://github.com/Brooooooklyn/canvas/issues/987
+test('draw-canvas-on-canvas', async (t) => {
+  const backCanvas = createCanvas(1920, 1080)
+  const backCtx = backCanvas.getContext('2d')
+
+  const picCanvas = createCanvas(640, 480)
+  const picCtx = picCanvas.getContext('2d')
+
+  backCtx.fillStyle = '#000000'
+  backCtx.fillRect(0, 0, 1920, 1080)
+
+  // load images from disk or from a URL
+  const catImage = await loadImage(join(__dirname, 'javascript.png'))
+
+  picCtx.drawImage(catImage, 0, 0, catImage.width, catImage.height)
+
+  backCtx.drawImage(picCanvas, 240, 0, 1440, 1080)
+
+  await snapshotImage(t, { ctx: backCtx, canvas: backCanvas })
+})

skia-c/skia_c.cpp

@@ -363,19 +363,25 @@ extern "C"
       int filter_quality,
       skiac_paint *c_paint)
   {
-    const auto src_rect = SkRect::MakeXYWH(sx, sy, s_width, s_height);
-    const auto dst_rect = SkRect::MakeXYWH(dx, dy, d_width, d_height);
     auto fq = enable_smoothing ? filter_quality : 0;
     const auto sampling = SamplingOptionsFromFQ(fq);
     auto paint = reinterpret_cast<const SkPaint *>(c_paint);
     if (is_canvas) {
-      auto srcSurface = reinterpret_cast<SkSurface *>(c_bitmap);
+      auto src_surface = reinterpret_cast<SkSurface *>(c_bitmap);
       CANVAS_CAST->save();
+      // Translate to the destination position
       CANVAS_CAST->translate(dx, dy);
-      CANVAS_CAST->clipRect(SkRect::MakeWH(d_width, d_height));
-      srcSurface->draw(CANVAS_CAST, -sx, -sy, sampling, paint);
+      // Scale using the ratio of destination size to source surface size
+      CANVAS_CAST->scale(
+          d_width / src_surface->width(),
+          d_height / src_surface->height()
+      );
+      // Draw the surface directly
+      src_surface->draw(CANVAS_CAST, -sx, -sy, sampling, paint);
       CANVAS_CAST->restore();
     } else {
+      const auto src_rect = SkRect::MakeXYWH(sx, sy, s_width, s_height);
+      const auto dst_rect = SkRect::MakeXYWH(dx, dy, d_width, d_height);
       CANVAS_CAST->drawImageRect(SkImages::RasterFromBitmap(*BITMAP_CAST), src_rect, dst_rect, sampling, paint, SkCanvas::kFast_SrcRectConstraint);
     }
   }