Revert of Use SkSwizzler to convert from CMYK

src/codec/SkJpegCodec.cpp

Index: src/codec/SkJpegCodec.cpp
diff --git a/src/codec/SkJpegCodec.cpp b/src/codec/SkJpegCodec.cpp
index 6850a7782512aa0cc731982c7fb3cff61c93b0ec..9975748cf4b4ce4010ea9dc79eca8cac6614fc93 100644
--- a/src/codec/SkJpegCodec.cpp
+++ b/src/codec/SkJpegCodec.cpp
@@ -21,6 +21,69 @@
 extern "C" {
     #include "jerror.h"
     #include "jpeglib.h"
+}
+
+/*
+ * Convert a row of CMYK samples to RGBA in place.
+ * Note that this method moves the row pointer.
+ * @param width the number of pixels in the row that is being converted
+ *              CMYK is stored as four bytes per pixel
+ */
+static void convert_CMYK_to_RGBA(uint8_t* row, uint32_t width) {
+    // We will implement a crude conversion from CMYK -> RGB using formulas
+    // from easyrgb.com.
+    //
+    // CMYK -> CMY
+    // C = C * (1 - K) + K
+    // M = M * (1 - K) + K
+    // Y = Y * (1 - K) + K
+    //
+    // libjpeg actually gives us inverted CMYK, so we must subtract the
+    // original terms from 1.
+    // CMYK -> CMY
+    // C = (1 - C) * (1 - (1 - K)) + (1 - K)
+    // M = (1 - M) * (1 - (1 - K)) + (1 - K)
+    // Y = (1 - Y) * (1 - (1 - K)) + (1 - K)
+    //
+    // Simplifying the above expression.
+    // CMYK -> CMY
+    // C = 1 - CK
+    // M = 1 - MK
+    // Y = 1 - YK
+    //
+    // CMY -> RGB
+    // R = (1 - C) * 255
+    // G = (1 - M) * 255
+    // B = (1 - Y) * 255
+    //
+    // Therefore the full conversion is below.  This can be verified at
+    // www.rapidtables.com (assuming inverted CMYK).
+    // CMYK -> RGB
+    // R = C * K * 255
+    // G = M * K * 255
+    // B = Y * K * 255
+    //
+    // As a final note, we have treated the CMYK values as if they were on
+    // a scale from 0-1, when in fact they are 8-bit ints scaling from 0-255.
+    // We must divide each CMYK component by 255 to obtain the true conversion
+    // we should perform.
+    // CMYK -> RGB
+    // R = C * K / 255
+    // G = M * K / 255
+    // B = Y * K / 255
+    for (uint32_t x = 0; x < width; x++, row += 4) {
+#if defined(SK_PMCOLOR_IS_RGBA)
+        row[0] = SkMulDiv255Round(row[0], row[3]);
+        row[1] = SkMulDiv255Round(row[1], row[3]);
+        row[2] = SkMulDiv255Round(row[2], row[3]);
+#else
+        uint8_t tmp = row[0];
+        row[0] = SkMulDiv255Round(row[2], row[3]);
+        row[1] = SkMulDiv255Round(row[1], row[3]);
+        row[2] = SkMulDiv255Round(tmp, row[3]);
+#endif
+        row[3] = 0xFF;
+    }
 }
 
 bool SkJpegCodec::IsJpeg(SkStream* stream) {
@@ -200,7 +263,10 @@
             return true;
         case kRGB_565_SkColorType:
             if (isCMYK) {
-                fDecoderMgr->dinfo()->out_color_space = JCS_CMYK;
+                // FIXME (msarett): We need to support 565 here.  It's not hard to do, considering
+                // we already convert CMYK to RGBA, I just need to do it.  I think it might be
+                // best to do this in SkSwizzler and also move convert_CMYK_to_RGBA into SkSwizzler.
+                return false;
             } else {
 #if defined(GOOGLE3)
                 return false;
@@ -299,22 +365,9 @@
     // If it's not, we want to know because it means our strategy is not optimal.
     SkASSERT(1 == dinfo->rec_outbuf_height);
 
-    if (JCS_CMYK == dinfo->out_color_space) {
-        this->initializeSwizzler(dstInfo, options);
-    }
-
     // Perform the decode a single row at a time
     uint32_t dstHeight = dstInfo.height();
-
-    JSAMPLE* dstRow;
-    if (fSwizzler) {
-        // write data to storage row, then sample using swizzler
-        dstRow = fSrcRow;
-    } else {
-        // write data directly to dst
-        dstRow = (JSAMPLE*) dst;
-    }
-
+    JSAMPLE* dstRow = (JSAMPLE*) dst;
     for (uint32_t y = 0; y < dstHeight; y++) {
         // Read rows of the image
         uint32_t lines = jpeg_read_scanlines(dinfo, &dstRow, 1);
@@ -326,13 +379,13 @@
             return fDecoderMgr->returnFailure("Incomplete image data", kIncompleteInput);
         }
 
-        if (fSwizzler) {
-            // use swizzler to sample row
-            fSwizzler->swizzle(dst, dstRow);
-            dst = SkTAddOffset<JSAMPLE>(dst, dstRowBytes);
-        } else {
-            dstRow = SkTAddOffset<JSAMPLE>(dstRow, dstRowBytes);
-        }
+        // Convert to RGBA if necessary
+        if (JCS_CMYK == dinfo->out_color_space) {
+            convert_CMYK_to_RGBA(dstRow, dstInfo.width());
+        }
+
+        // Move to the next row
+        dstRow = SkTAddOffset<JSAMPLE>(dstRow, dstRowBytes);
     }
 
     return kSuccess;
@@ -340,30 +393,26 @@
 
 void SkJpegCodec::initializeSwizzler(const SkImageInfo& dstInfo, const Options& options) {
     SkSwizzler::SrcConfig srcConfig = SkSwizzler::kUnknown;
-    if (JCS_CMYK == fDecoderMgr->dinfo()->out_color_space) {
-        srcConfig = SkSwizzler::kCMYK;
-    } else {
-        switch (dstInfo.colorType()) {
-            case kGray_8_SkColorType:
-                srcConfig = SkSwizzler::kGray;
-                break;
-            case kRGBA_8888_SkColorType:
-                srcConfig = SkSwizzler::kRGBX;
-                break;
-            case kBGRA_8888_SkColorType:
-                srcConfig = SkSwizzler::kBGRX;
-                break;
-            case kRGB_565_SkColorType:
-                srcConfig = SkSwizzler::kRGB_565;
-                break;
-            default:
-                // This function should only be called if the colorType is supported by jpeg
+    switch (dstInfo.colorType()) {
+        case kGray_8_SkColorType:
+            srcConfig = SkSwizzler::kGray;
+            break;
+        case kRGBA_8888_SkColorType:
+            srcConfig = SkSwizzler::kRGBX;
+            break;
+        case kBGRA_8888_SkColorType:
+            srcConfig = SkSwizzler::kBGRX;
+            break;
+        case kRGB_565_SkColorType:
+            srcConfig = SkSwizzler::kRGB_565;
+            break;
+        default:
+            // This function should only be called if the colorType is supported by jpeg
 #if defined(GOOGLE3)
-                SK_CRASH();
+            SK_CRASH();
 #else
-                SkASSERT(false);
+            SkASSERT(false);
 #endif
-        }
     }
 
     fSwizzler.reset(SkSwizzler::CreateSwizzler(srcConfig, nullptr, dstInfo, options));
@@ -405,9 +454,8 @@
         return kInvalidInput;
     }
 
-    // We will need a swizzler if we are performing a subset decode or
-    // converting from CMYK.
-    if (options.fSubset || JCS_CMYK == fDecoderMgr->dinfo()->out_color_space) {
+    // We will need a swizzler if we are performing a subset decode
+    if (options.fSubset) {
         this->initializeSwizzler(dstInfo, options);
     }
 
@@ -437,7 +485,12 @@
             return y;
         }
 
-        if (fSwizzler) {
+        // Convert to RGBA if necessary
+        if (JCS_CMYK == fDecoderMgr->dinfo()->out_color_space) {
+            convert_CMYK_to_RGBA(dstRow, fDecoderMgr->dinfo()->output_width);
+        }
+
+        if(fSwizzler) {
             // use swizzler to sample row
             fSwizzler->swizzle(dst, dstRow);
             dst = SkTAddOffset<JSAMPLE>(dst, rowBytes);