Non DCTSIZE multiple width support for JPEG YUV decoding

Source/platform/image-decoders/jpeg/JPEGImageDecoder.cpp

Index: Source/platform/image-decoders/jpeg/JPEGImageDecoder.cpp
diff --git a/Source/platform/image-decoders/jpeg/JPEGImageDecoder.cpp b/Source/platform/image-decoders/jpeg/JPEGImageDecoder.cpp
index cfa029567b0d29266eea09b72f5d271018fd003d..47ea1df071cd9ded4689ab3eb42fd520612f02cc 100644
--- a/Source/platform/image-decoders/jpeg/JPEGImageDecoder.cpp
+++ b/Source/platform/image-decoders/jpeg/JPEGImageDecoder.cpp
@@ -252,11 +252,12 @@ static void readColorProfile(jpeg_decompress_struct* info, ColorProfile& colorPr
 }
 #endif
 
-static IntSize computeUVSize(const jpeg_decompress_struct* info)
+static IntSize computeYUVSize(const jpeg_decompress_struct* info, int component, bool memoryAllocation)
 {
-    int h = info->cur_comp_info[0]->h_samp_factor;
-    int v = info->cur_comp_info[0]->v_samp_factor;
-    return IntSize((info->output_width + h - 1) / h, (info->output_height + v - 1) / v);
+    if (memoryAllocation) {
+        return IntSize(info->cur_comp_info[component]->width_in_blocks * DCTSIZE, info->cur_comp_info[component]->height_in_blocks * DCTSIZE);
+    }
+    return IntSize(info->cur_comp_info[component]->downsampled_width, info->cur_comp_info[component]->downsampled_height);
 }
 
 static yuv_subsampling yuvSubsampling(const jpeg_decompress_struct& info)
@@ -475,6 +476,7 @@ public:
             if (overrideColorSpace == JCS_YCbCr) {
                 m_info.out_color_space = JCS_YCbCr;
                 m_info.raw_data_out = TRUE;
+                m_uvSize = computeYUVSize(&m_info, 1, true); // U size and V size have to be the same if we got here

[sugoi1, 2014/09/05 20:14:57]

This is unfortunate, but I have to cache this value here, because this data can
be erased or modified if jpeg_consume_input() is called (see progressive case
for an example).

[Noel Gordon, 2014/09/08 16:13:32]

"// U size and V size have to be the same if we got here"

not quite sure what that comment means.

[sugoi1, 2014/09/09 15:08:15]

If we have reached this point in the code, it means overrideColorSpace is
JCS_YCbCr, which means yuvSubsampling(m_info) != YUV_UNKNOWN, which means that
the sizes of U and V are the same, because, for now, having different sizes for
the U and V components is not supported.

             }
 
             // Don't allocate a giant and superfluous memory buffer when the
@@ -596,6 +598,7 @@ public:
     jpeg_decompress_struct* info() { return &m_info; }
     JSAMPARRAY samples() const { return m_samples; }
     JPEGImageDecoder* decoder() { return m_decoder; }
+    IntSize uvSize() const { return m_uvSize; }
 #if USE(QCMSLIB)
     qcms_transform* colorTransform() const { return m_transform; }
 
@@ -638,6 +641,8 @@ private:
 
     JSAMPARRAY m_samples;
 
+    IntSize m_uvSize;
+
 #if USE(QCMSLIB)
     qcms_transform* m_transform;
 #endif
@@ -712,12 +717,12 @@ void JPEGImageDecoder::setDecodedSize(unsigned width, unsigned height)
     m_decodedSize = IntSize(width, height);
 }
 
-IntSize JPEGImageDecoder::decodedYUVSize(int component) const
+IntSize JPEGImageDecoder::decodedYUVSize(int component, bool memoryAllocation) const
 {
-    if (((component == 1) || (component == 2)) && m_reader.get()) { // Asking for U or V
+    if (((component >= 0) && (component <= 2)) && m_reader.get()) {

[Noel Gordon, 2014/09/08 16:13:33]

nit: m_reader.get() -> m_reader

[sugoi1, 2014/09/09 15:08:15]

Done.

         const jpeg_decompress_struct* info = m_reader->info();
         if (info && (info->out_color_space == JCS_YCbCr)) {

[Noel Gordon, 2014/09/08 16:13:32]

nit: info() is never null

[sugoi1, 2014/09/09 15:08:15]

Done.

-            return computeUVSize(info);
+            return computeYUVSize(info, component, memoryAllocation);
         }
     }
 
@@ -855,7 +860,7 @@ static bool outputRawData(JPEGImageReader* reader, ImagePlanes* imagePlanes)
     int yHeight = info->output_height;
     int yMaxH = yHeight - 1;
     int v = info->cur_comp_info[0]->v_samp_factor;
-    IntSize uvSize = computeUVSize(info);
+    IntSize uvSize = reader->uvSize();
     int uvMaxH = uvSize.height() - 1;
     JSAMPROW outputY = static_cast<JSAMPROW>(imagePlanes->plane(0));
     JSAMPROW outputU = static_cast<JSAMPROW>(imagePlanes->plane(1));