Optimizes JPEGCodec for libjpeg-turbo

Libjpeg-turbo can use RGBA and BGRA pixels used by Chromium as its input or output. This change uses these converters to avoid memory copies when the output format is RGBA or BGRA.

BUG=none
TEST=none
Review URL: http://codereview.chromium.org/6603010

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@77444 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 73 insertions, 0 deletions

diff --git a/ui/gfx/codec/jpeg_codec.cc b/ui/gfx/codec/jpeg_codec.cc
index 0558c93..757686b 100644
--- a/ui/gfx/codec/jpeg_codec.cc
+++ b/ui/gfx/codec/jpeg_codec.cc
@@ -216,7 +216,31 @@ bool JPEGCodec::Encode(const unsigned char* input, ColorFormat format,
   cinfo.image_width = w;
   cinfo.image_height = h;
   cinfo.input_components = 3;
+#ifdef JCS_EXTENSIONS
+  // Choose an input colorspace and return if it is an unsupported one. Since
+  // libjpeg-turbo supports all input formats used by Chromium (i.e. RGB, RGBA,
+  // and BGRA), we just map the input parameters to a colorspace used by
+  // libjpeg-turbo.
+  if (format == FORMAT_RGB) {
+    cinfo.input_components = 3;
+    cinfo.in_color_space = JCS_RGB;
+  } else if (format == FORMAT_RGBA ||
+             format == FORMAT_SkBitmap && SK_R32_SHIFT == 0) {
+    cinfo.input_components = 4;
+    cinfo.in_color_space = JCS_EXT_RGBX;
+  } else if (format == FORMAT_BGRA ||
+             format == FORMAT_SkBitmap && SK_B32_SHIFT == 0) {
+    cinfo.input_components = 4;
+    cinfo.in_color_space = JCS_EXT_BGRX;
+  } else {
+    // We can exit this function without calling jpeg_destroy_compress() because
+    // CompressDestroyer automaticaly calls it.
+    NOTREACHED() << "Invalid pixel format";
+    return false;
+  }
+#else
   cinfo.in_color_space = JCS_RGB;
+#endif
   cinfo.data_precision = 8;
 
   jpeg_set_defaults(&cinfo);
@@ -235,6 +259,15 @@ bool JPEGCodec::Encode(const unsigned char* input, ColorFormat format,
   jpeg_start_compress(&cinfo, 1);
 
   // feed it the rows, doing necessary conversions for the color format
+#ifdef JCS_EXTENSIONS
+  // This function already returns when the input format is not supported by
+  // libjpeg-turbo and needs conversion. Therefore, we just encode lines without
+  // conversions.
+  while (cinfo.next_scanline < cinfo.image_height) {
+    const unsigned char* row = &input[cinfo.next_scanline * row_byte_width];
+    jpeg_write_scanlines(&cinfo, const_cast<unsigned char**>(&row), 1);
+  }
+#else
   if (format == FORMAT_RGB) {
     // no conversion necessary
     while (cinfo.next_scanline < cinfo.image_height) {
@@ -264,6 +297,7 @@ bool JPEGCodec::Encode(const unsigned char* input, ColorFormat format,
     }
     delete[] row;
   }
+#endif
 
   jpeg_finish_compress(&cinfo);
   return true;
@@ -446,7 +480,31 @@ bool JPEGCodec::Decode(const unsigned char* input, size_t input_size,
     case JCS_GRAYSCALE:
     case JCS_RGB:
     case JCS_YCbCr:
+#ifdef JCS_EXTENSIONS
+      // Choose an output colorspace and return if it is an unsupported one.
+      // Same as JPEGCodec::Encode(), libjpeg-turbo supports all input formats
+      // used by Chromium (i.e. RGB, RGBA, and BGRA) and we just map the input
+      // parameters to a colorspace.
+      if (format == FORMAT_RGB) {
+        cinfo.out_color_space = JCS_RGB;
+        cinfo.output_components = 3;
+      } else if (format == FORMAT_RGBA ||
+                 format == FORMAT_SkBitmap && SK_R32_SHIFT == 0) {
+        cinfo.out_color_space = JCS_EXT_RGBX;
+        cinfo.output_components = 4;
+      } else if (format == FORMAT_BGRA ||
+                 format == FORMAT_SkBitmap && SK_B32_SHIFT == 0) {
+        cinfo.out_color_space = JCS_EXT_BGRX;
+        cinfo.output_components = 4;
+      } else {
+        // We can exit this function without calling jpeg_destroy_decompress()
+        // because DecompressDestroyer automaticaly calls it.
+        NOTREACHED() << "Invalid pixel format";
+        return false;
+      }
+#else
       cinfo.out_color_space = JCS_RGB;
+#endif
       break;
     case JCS_CMYK:
     case JCS_YCCK:
@@ -456,7 +514,9 @@ bool JPEGCodec::Decode(const unsigned char* input, size_t input_size,
       // care about these anyway.
       return false;
   }
+#ifndef JCS_EXTENSIONS
   cinfo.output_components = 3;
+#endif
 
   jpeg_calc_output_dimensions(&cinfo);
   *w = cinfo.output_width;
@@ -468,6 +528,18 @@ bool JPEGCodec::Decode(const unsigned char* input, size_t input_size,
   // how to align row lengths as we do for the compressor.
   int row_read_stride = cinfo.output_width * cinfo.output_components;
 
+#ifdef JCS_EXTENSIONS
+  // Create memory for a decoded image and write decoded lines to the memory
+  // without conversions same as JPEGCodec::Encode().
+  int row_write_stride = row_read_stride;
+  output->resize(row_write_stride * cinfo.output_height);
+
+  for (int row = 0; row < static_cast<int>(cinfo.output_height); row++) {
+    unsigned char* rowptr = &(*output)[row * row_write_stride];
+    if (!jpeg_read_scanlines(&cinfo, &rowptr, 1))
+      return false;
+  }
+#else
   if (format == FORMAT_RGB) {
     // easy case, row needs no conversion
     int row_write_stride = row_read_stride;
@@ -508,6 +580,7 @@ bool JPEGCodec::Decode(const unsigned char* input, size_t input_size,
       converter(rowptr, *w, &(*output)[row * row_write_stride]);
     }
   }
+#endif
 
   jpeg_finish_decompress(&cinfo);
   jpeg_destroy_decompress(&cinfo);