Changeset 279424 in webkit

Timestamp:

Jun 30, 2021 11:29:02 AM (13 months ago)

Author:

commit-queue@webkit.org

Message:

toDataURL image upside down if premultipliedAlpha=false
​https://bugs.webkit.org/show_bug.cgi?id=156129
<rdar://problem/53942867>

Patch by Kimmo Kinnunen <​kkinnunen@apple.com> on 2021-06-30
Reviewed by Kenneth Russell.

Flip the result PixelBuffer of GraphicsContextGL::paintRenderingResultsToPixelBuffer()
along the y-axis manually with memcpy.
ReadPixels returns the pixels upside down.
The PixelBuffer code-path is only used for reading unpremultiplied
image contents so that toDataURL() can encode the premultipliedAlpha=false
WebGL content as was rendered.

Other code-paths, such as Context2D.drawImage and drawing to the document,
use GraphicsContextGL::paintRenderingResultsToCanvas().
In those cases y-flip is done by constructing a ImageBuffer for the PixelBuffer
and then using y-flip transform to draw the ImageBuffer to the target ImageBuffer
using GraphicsContext.

Fixes webgl/1.0.x/conformance/canvas/to-data-url-test.html

• platform/graphics/opengl/GraphicsContextGLOpenGL.cpp:

(WebCore::GraphicsContextGLOpenGL::paintRenderingResultsToPixelBuffer):

Location:

trunk

Files:

• LayoutTests/TestExpectations (modified) (1 diff)
• Source/WebCore/ChangeLog (modified) (1 diff)
• Source/WebCore/platform/graphics/opengl/GraphicsContextGLOpenGL.cpp (modified) (2 diffs)

trunk/LayoutTests/TestExpectations

@@ -3503 +3503 @@
 webgl/1.0.x [ Skip ]
 
+# Explicitly enable tests which we have fixed and do not have corresponding 1.0.3 test functionality.
+webgl/1.0.x/conformance/canvas/to-data-url-test.html [ Pass ]
+
 # WebGL conformance test suite 2.0.1 is skipped until 2.0.0 is retired.
 webgl/2.0.y [ Skip ]
+
+# Explicitly enable tests which we have fixed and do not have corresponding 2.0.y test functionality.
+webgl/2.0.y/conformance/canvas/to-data-url-test.html [ Pass ]
 
 # pre-wrap progression. Other rendering engines agree with the result.

trunk/Source/WebCore/ChangeLog

@@ +1 @@
+2021-06-30  Kimmo Kinnunen  <kkinnunen@apple.com>
+
+        toDataURL image upside down if premultipliedAlpha=false
+        https://bugs.webkit.org/show_bug.cgi?id=156129
+        <rdar://problem/53942867>
+
+        Reviewed by Kenneth Russell.
+
+        Flip the result `PixelBuffer` of `GraphicsContextGL::paintRenderingResultsToPixelBuffer()`
+        along the y-axis manually with memcpy.
+        ReadPixels returns the pixels upside down.
+        The `PixelBuffer` code-path is only used for reading unpremultiplied
+        image contents so that `toDataURL()` can encode the premultipliedAlpha=false
+        WebGL content as was rendered.
+
+        Other code-paths, such as Context2D.drawImage and drawing to the document,
+        use `GraphicsContextGL::paintRenderingResultsToCanvas()`.
+        In those cases y-flip is done by constructing a `ImageBuffer` for the PixelBuffer
+        and then using y-flip transform to draw the `ImageBuffer` to the target `ImageBuffer`
+        using `GraphicsContext`.
+
+        Fixes webgl/1.0.x/conformance/canvas/to-data-url-test.html
+
+        * platform/graphics/opengl/GraphicsContextGLOpenGL.cpp:
+        (WebCore::GraphicsContextGLOpenGL::paintRenderingResultsToPixelBuffer):
+
 2021-06-30  Antoine Quint  <graouts@webkit.org>
 

trunk/Source/WebCore/platform/graphics/opengl/GraphicsContextGLOpenGL.cpp

@@ -40 +40 @@
 #include "GraphicsContextGLCV.h"
 #endif
+
+#include <memory>
 
 namespace WebCore {
@@ -233 +235 @@
     if (contextAttributes().premultipliedAlpha)
         return std::nullopt;
-    return readRenderingResultsForPainting();
+    auto results = readRenderingResultsForPainting();
+    if (results && !results->size().isEmpty()) {
+        ASSERT(results->format().pixelFormat == PixelFormat::RGBA8 || results->format().pixelFormat == PixelFormat::BGRA8);
+        // FIXME: Make PixelBufferConversions support negative rowBytes and in-place conversions.
+        const auto size = results->size();
+        const size_t rowStride = size.width() * 4;
+        uint8_t* top = results->data().data();
+        uint8_t* bottom = top + (size.height() - 1) * rowStride;
+        std::unique_ptr<uint8_t[]> temp(new uint8_t[rowStride]);
+        for (; top < bottom; top += rowStride, bottom -= rowStride) {
+            memcpy(temp.get(), bottom, rowStride);
+            memcpy(bottom, top, rowStride);
+            memcpy(top, temp.get(), rowStride);
+        }
+    }
+    return results;
 }