Changeset 46931 in webkit

Timestamp:

Aug 7, 2009 5:03:21 PM (15 years ago)

Author:

abarth@webkit.org

Message:

2009-08-07 Nicolas Weber <​thakis@chromium.org>

Teach WebKit how to decode jpegs in cmyk and ycck color spaces.
Heavily inspired by Firefox's take on this issue.

​https://bugs.webkit.org/show_bug.cgi?id=27909

Reviewed by Eric Seidel.

• platform/image-decoders/jpeg/JPEGImageDecoder.cpp: (WebCore::JPEGImageReader::decode): Tell jpeglib to convert ycck to cmyk and keep cmyk. (WebCore::convertCMYKToRGBA): Added function to convert cmyk to rgb. (WebCore::convertRGBToRGBA): Extracted existing conversion logic into its own function. (WebCore::JPEGImageDecoder::outputScanlines): Call convertCMYKToRGBA for cmyk images, convertRGBToRGBA for rgb images.

Location:

trunk/WebCore

Files:

• ChangeLog (modified) (1 diff)
• platform/image-decoders/jpeg/JPEGImageDecoder.cpp (modified) (3 diffs)

trunk/WebCore/ChangeLog

@@ +1 @@
+2009-08-07  Nicolas Weber  <thakis@chromium.org>
+
+        Teach WebKit how to decode jpegs in cmyk and ycck color spaces.
+        Heavily inspired by Firefox's take on this issue.
+
+        https://bugs.webkit.org/show_bug.cgi?id=27909
+
+        Reviewed by Eric Seidel.
+
+        * platform/image-decoders/jpeg/JPEGImageDecoder.cpp:
+        (WebCore::JPEGImageReader::decode):
+        Tell jpeglib to convert ycck to cmyk and keep cmyk.
+        (WebCore::convertCMYKToRGBA):
+        Added function to convert cmyk to rgb.
+        (WebCore::convertRGBToRGBA):
+        Extracted existing conversion logic into its own function.
+        (WebCore::JPEGImageDecoder::outputScanlines):
+        Call convertCMYKToRGBA for cmyk images, convertRGBToRGBA for rgb
+        images.
+
 2009-08-07  Drew Wilson  <atwilson@google.com>
 

trunk/WebCore/platform/image-decoders/jpeg/JPEGImageDecoder.cpp

@@ -195 +195 @@
                     case JCS_CMYK:
                     case JCS_YCCK:
+                        // jpeglib cannot convert these to rgb, but it can
+                        // convert ycck to cmyk
+                        m_info.out_color_space = JCS_CMYK;
+                        break;
                     default:
                         m_state = JPEG_ERROR;
@@ -458 +462 @@
 }
 
+static void convertCMYKToRGBA(RGBA32Buffer& dest, JSAMPROW src, jpeg_decompress_struct* info)
+{
+    ASSERT(info->out_color_space == JCS_CMYK);
+
+    for (unsigned x = 0; x < info->output_width; ++x) {
+        unsigned c = *src++;
+        unsigned m = *src++;
+        unsigned y = *src++;
+        unsigned k = *src++;
+
+        // Source is 'Inverted CMYK', output is RGB.
+        // See: http://www.easyrgb.com/math.php?MATH=M12#text12
+        // Or:  http://www.ilkeratalay.com/colorspacesfaq.php#rgb
+
+        // From CMYK to CMY
+        // C = C * ( 1 - K ) + K
+        // M = M * ( 1 - K ) + K
+        // Y = Y * ( 1 - K ) + K
+
+        // From Inverted CMYK to CMY is thus:
+        // C = (1-iC) * (1 - (1-iK)) + (1-iK) => 1 - iC*iK
+        // Same for M and Y
+
+        // Convert from CMY (0..1) to RGB (0..1)
+        // R = 1 - C => 1 - (1 - iC*iK) => iC*iK
+        // G = 1 - M => 1 - (1 - iM*iK) => iM*iK
+        // B = 1 - Y => 1 - (1 - iY*iK) => iY*iK
+
+        // read_scanlines has increased the scanline counter, so we
+        // actually mean the previous one.
+        dest.setRGBA(x, info->output_scanline - 1, c * k / 255, m * k / 255, y * k / 255, 0xFF);
+    }
+}
+
+static void convertRGBToRGBA(RGBA32Buffer& dest, JSAMPROW src, jpeg_decompress_struct* info)
+{
+    ASSERT(info->out_color_space == JCS_RGB);
+
+    for (unsigned x = 0; x < info->output_width; ++x) {
+        unsigned r = *src++;
+        unsigned g = *src++;
+        unsigned b = *src++;
+        // read_scanlines has increased the scanline counter, so we
+        // actually mean the previous one.
+        dest.setRGBA(x, info->output_scanline - 1, r, g, b, 0xFF);
+    }
+}
+
 bool JPEGImageDecoder::outputScanlines()
 {
@@ -484 +536 @@
         if (jpeg_read_scanlines(info, samples, 1) != 1)
             return false;
-        JSAMPLE *j1 = samples[0];
-        for (unsigned x = 0; x < info->output_width; ++x) {
-            unsigned r = *j1++;
-            unsigned g = *j1++;
-            unsigned b = *j1++;
-            // read_scanlines has increased the scanline counter, so we
-            // actually mean the previous one.
-            buffer.setRGBA(x, info->output_scanline - 1, r, g, b, 0xFF);
-        }
+
+        if (info->out_color_space == JCS_RGB)
+            convertRGBToRGBA(buffer, *samples, info);
+        else if (info->out_color_space == JCS_CMYK)
+            convertCMYKToRGBA(buffer, *samples, info);
+        else
+            return false;
     }