Allow decoding JPEG into A8.

src/images/SkImageDecoder_libjpeg.cpp

 
 /*
  * Copyright 2007 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 
 #include "SkImageDecoder.h"
@@ skipping 271 matching lines @@
     cinfo.scale_denom = sampleSize;
 
     /* this gives about 30% performance improvement. In theory it may
        reduce the visual quality, in practice I'm not seeing a difference
      */
     cinfo.do_fancy_upsampling = 0;
 
     /* this gives another few percents */
     cinfo.do_block_smoothing = 0;
 
+    SrcDepth srcDepth = k32Bit_SrcDepth;
     /* default format is RGB */
     if (cinfo.jpeg_color_space == JCS_CMYK) {
         // libjpeg cannot convert from CMYK to RGB - here we set up
         // so libjpeg will give us CMYK samples back and we will
         // later manually convert them to RGB
         cinfo.out_color_space = JCS_CMYK;
+    } else if (cinfo.jpeg_color_space == JCS_GRAYSCALE) {
+        cinfo.out_color_space = JCS_GRAYSCALE;
+        srcDepth = k8BitGray_SrcDepth;
     } else {
         cinfo.out_color_space = JCS_RGB;
     }
 
-    SkBitmap::Config config = this->getPrefConfig(k32Bit_SrcDepth, false);
+    SkBitmap::Config config = this->getPrefConfig(srcDepth, false);
     // only these make sense for jpegs
-    if (config != SkBitmap::kARGB_8888_Config &&
-        config != SkBitmap::kARGB_4444_Config &&
-        config != SkBitmap::kRGB_565_Config) {
+    if (SkBitmap::kA8_Config == config) {
+        if (cinfo.jpeg_color_space != JCS_GRAYSCALE) {
+            // Converting from a non grayscale image to A8 is
+            // not currently supported.
+            config = SkBitmap::kARGB_8888_Config;
+            // Change the output from jpeg back to RGB.
+            cinfo.out_color_space = JCS_RGB;
+        }
+    } else if (config != SkBitmap::kARGB_8888_Config &&
+               config != SkBitmap::kARGB_4444_Config &&
+               config != SkBitmap::kRGB_565_Config) {
         config = SkBitmap::kARGB_8888_Config;
     }
 
 #ifdef ANDROID_RGB
     cinfo.dither_mode = JDITHER_NONE;
     if (SkBitmap::kARGB_8888_Config == config && JCS_CMYK != cinfo.out_color_space) {
         cinfo.out_color_space = JCS_RGBA_8888;
     } else if (SkBitmap::kRGB_565_Config == config && JCS_CMYK != cinfo.out_color_space) {
         cinfo.out_color_space = JCS_RGB_565;
         if (this->getDitherImage()) {
@@ skipping 692 matching lines @@
 }
 
 static SkImageEncoder* sk_libjpeg_efactory(SkImageEncoder::Type t) {
     return (SkImageEncoder::kJPEG_Type == t) ? SkNEW(SkJPEGImageEncoder) : NULL;
 }
 
 
 static SkTRegistry<SkImageDecoder*, SkStream*> gDReg(sk_libjpeg_dfactory);
 static SkTRegistry<SkImageDecoder::Format, SkStream*> gFormatReg(get_format_jpeg);
 static SkTRegistry<SkImageEncoder*, SkImageEncoder::Type> gEReg(sk_libjpeg_efactory);