Create SkColorSpaceXform to handle color conversions

dm/DMSrcSink.cpp

Index: dm/DMSrcSink.cpp
diff --git a/dm/DMSrcSink.cpp b/dm/DMSrcSink.cpp
index f99afe48597247dd015f8c69d3aa1192a5ea39a4..5d5dc58cff82cc3807943166bb3f9ec2842bfdec 100644
--- a/dm/DMSrcSink.cpp
+++ b/dm/DMSrcSink.cpp
@@ -9,10 +9,12 @@
 #include "SkAndroidCodec.h"
 #include "SkCodec.h"
 #include "SkCodecImageGenerator.h"
+#include "SkColorSpaceXform.h"
 #include "SkCommonFlags.h"
 #include "SkData.h"
 #include "SkDocument.h"
 #include "SkError.h"
+#include "SkHalf.h"
 #include "SkImageGenerator.h"
 #include "SkImageGeneratorCG.h"
 #include "SkImageGeneratorWIC.h"
@@ -942,6 +944,17 @@ bool ColorCodecSrc::veto(SinkFlags flags) const {
     return flags.type != SinkFlags::kRaster || flags.approach != SinkFlags::kDirect;
 }
 
+static uint8_t clampFloatToByte(float v) {
+    v = v * 255.0f;
+    if (v > 255.0f) {
+        return 255;
+    } else if (v < 0.0f) {
+        return 0;
+    } else {
+        return (uint8_t) (v + 0.5f);
+    }
+}
+
 Error ColorCodecSrc::draw(SkCanvas* canvas) const {
     if (kRGB_565_SkColorType == canvas->imageInfo().colorType()) {
         return Error::Nonfatal("No need to test color correction to 565 backend.");
@@ -957,24 +970,102 @@ Error ColorCodecSrc::draw(SkCanvas* canvas) const {
         return SkStringPrintf("Couldn't create codec for %s.", fPath.c_str());
     }
 
-    SkImageInfo decodeInfo = codec->getInfo().makeColorType(kN32_SkColorType);
+    SkImageInfo info = codec->getInfo().makeColorType(kN32_SkColorType);
+    uint32_t width = info.width();
+    uint32_t height = info.height();
     SkBitmap bitmap;
-    if (!bitmap.tryAllocPixels(decodeInfo)) {
+    if (!bitmap.tryAllocPixels(info)) {
         return SkStringPrintf("Image(%s) is too large (%d x %d)", fPath.c_str(),
-                              decodeInfo.width(), decodeInfo.height());
+                              info.width(), info.height());
+    }
+
+    SkImageInfo decodeInfo = info;
+    if (kBaseline_Mode != fMode) {
+        decodeInfo = decodeInfo.makeColorType(kRGBA_8888_SkColorType);
+    }
+
+    SkCodec::Result r = codec->getPixels(decodeInfo, bitmap.getPixels(), bitmap.rowBytes());
+    if (SkCodec::kSuccess != r) {
+        return SkStringPrintf("Couldn't getPixels %s. Error code %d", fPath.c_str(), r);
     }
 
     switch (fMode) {
         case kBaseline_Mode:
-            switch (codec->getPixels(decodeInfo, bitmap.getPixels(), bitmap.rowBytes())) {
-                case SkCodec::kSuccess:
-                    break;
-                default:
-                    // Everything else is considered a failure.
-                    return SkStringPrintf("Couldn't getPixels %s.", fPath.c_str());
+            canvas->drawBitmap(bitmap, 0, 0);
+            break;
+        case kSrcToLinear_Mode: {
+            sk_sp<SkColorSpace> srcSpace = sk_ref_sp(codec->getColorSpace());

[scroggo, 2016/05/05 20:57:26]

Should we update the API to return a const sk_sp<SkColorSpace>& ? Then you won't
need to call sk_ref_sp, IIUC.

[msarett, 2016/05/05 21:34:26]

We *should* do that.  We actually can't because SkColorSpace.h isn't in include,
and we forward declare it in SkCodec.h.

I don't think we can make this change until SkColorSpace.h moves to include.

+            if (!srcSpace) {
+                return SkStringPrintf("Cannot test color correction without a src profile.");
+            }
+
+            SkAutoTDelete<SkColorSpaceXform> xform(SkColorSpaceXform::New(srcSpace, nullptr,
+                    SkColorSpaceXform::kSrcToLinear_Op));
+            if (!xform) {
+                return Error::Nonfatal("Xform is not implemented yet.");

[scroggo, 2016/05/05 20:57:26]

Alternatively, should we only upload an image for this test once this is
implemented?

[msarett, 2016/05/05 21:34:26]

I believe that's how it works now.

The only images in kSrcToLinear_Mode that will be uploaded are those where we
have implemented the transform.

[scroggo, 2016/05/06 13:50:00]

In that case, shouldn't this be a fatal error?

             }
+
+            // Create a F16 destination buffer for the output of color conversion.
+            size_t rowBytes = width * SkColorTypeBytesPerPixel(kRGBA_F16_SkColorType);
+            SkAutoMalloc pixels(rowBytes * height);
+
+            // Apply the conversion to linear F16 pixels.
+            SkISize size = SkISize::Make(width, height);
+            xform->apply(pixels.get(), bitmap.getPixels(), size, rowBytes, bitmap.rowBytes());
+
+            // Converting to a linear color space is useful because most post-decode operations
+            // assume linear pixels (ex: scaling, premultiplying, etc).  However, we will want
+            // to be in a non-linear dst color space when we write the pixels to the screen.

[scroggo, 2016/05/05 20:57:26]

It's strange that we are talking about writing to a screen when this test never
does that.

Instead, we'll write a new PNG (without color correction?) that you'll later
look at on a screen in Gold (which may or may not do color correction?). Is that
all okay?

[msarett, 2016/05/05 21:34:26]

Agreed I'll go back and explain this further...

We are writing to unmarked pngs.  We hope that the browser will not do any color
correction on the unmarked pngs.

It's likely that it will assume unmarked means sRGB and that the monitor is sRGB
(so no correction).  I think we'd still be ok if the monitor is non-sRGB, but
the browser does some correction from sRGB to the monitor space - this would be
weird though...

+            // In order to test, we will assume that the dst wants sRGB pixels and convert the
+            // linear intermediate to sRGB.  This will make the output images look normal (or
+            // prettier than normal) if there are no bugs in our conversions.
+            uint64_t* rowPtr = (uint64_t*) pixels.get();
+            for (uint32_t y = 0; y < height; y++) {
+                for (uint32_t x = 0; x < width; x++) {
+                    // Extract floats.
+                    uint64_t pixel = rowPtr[x];
+                    float linearR = SkHalfToFloat((pixel >>  0) & 0xFFFF);
+                    float linearG = SkHalfToFloat((pixel >> 16) & 0xFFFF);
+                    float linearB = SkHalfToFloat((pixel >> 32) & 0xFFFF);
+                    float linearA = SkHalfToFloat((pixel >> 48) & 0xFFFF);
+
+                    // Currently we only support decodes to F16 when the encoded image has
+                    // a color space.
+                    SkColorSpace* colorSpace = codec->getColorSpace();
+                    SkASSERT(colorSpace);
+
+                    // Convert to XYZ gamut.
+                    const SkMatrix44& toXYZ = colorSpace->xyz();
+                    float xyzR = linearR*toXYZ.getFloat(0, 0) + linearG*toXYZ.getFloat(1, 0) +
+                                 linearB*toXYZ.getFloat(2, 0) + toXYZ.getFloat(3, 0);
+                    float xyzG = linearR*toXYZ.getFloat(0, 1) + linearG*toXYZ.getFloat(1, 1) +
+                                 linearB*toXYZ.getFloat(2, 1) + toXYZ.getFloat(3, 1);
+                    float xyzB = linearR*toXYZ.getFloat(0, 2) + linearG*toXYZ.getFloat(1, 2) +
+                                 linearB*toXYZ.getFloat(2, 2) + toXYZ.getFloat(3, 2);
+
+                    // Convert to sRGB gamut, using inverse sRGB matrix.
+                    float dstR = xyzR*3.13651f + xyzG*-1.61902f + xyzB*-0.490837f;
+                    float dstG = xyzR*-0.978981f + xyzG*1.91625f + xyzB*0.0334349f;
+                    float dstB = xyzR*0.072085f + xyzG*-0.229113f + xyzB*1.40577f;
+
+                    // Convert to sRGB gamma.
+                    float curveR = pow(dstR, 1.0f/2.2f);
+                    float curveG = pow(dstG, 1.0f/2.2f);
+                    float curveB = pow(dstB, 1.0f/2.2f);
+
+                    uint32_t* ptr = (uint32_t*) bitmap.getAddr(x, y);
+                    *ptr = SkPackARGB32NoCheck(clampFloatToByte(linearA),
+                                               clampFloatToByte(curveR),
+                                               clampFloatToByte(curveG),
+                                               clampFloatToByte(curveB));
+                }
+
+                rowPtr = SkTAddOffset<uint64_t>(rowPtr, rowBytes);
+            }
+
             canvas->drawBitmap(bitmap, 0, 0);
             break;
+        }
         default:
             SkASSERT(false);
             return "Invalid fMode";