Gamma correction for distance field text.

src/core/SkPaint.cpp

 /*
  * Copyright 2006 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 "SkPaint.h"
 #include "SkAnnotation.h"
 #include "SkAutoKern.h"
@@ skipping 1755 matching lines @@
     SkSafeUnref(gMaskGamma);
     gMaskGamma = NULL;
     SkDEBUGCODE(gContrast = SK_ScalarMin;)
     SkDEBUGCODE(gPaintGamma = SK_ScalarMin;)
     SkDEBUGCODE(gDeviceGamma = SK_ScalarMin;)
 }
 
 /**
  *  We ensure that the rec is self-consistent and efficient (where possible)
  */
-void SkScalerContext::PostMakeRec(const SkPaint&, SkScalerContext::Rec* rec) {
+void SkScalerContext::PostMakeRec(const SkPaint& paint, SkScalerContext::Rec* rec) {
     /**
      *  If we're asking for A8, we force the colorlum to be gray, since that
      *  limits the number of unique entries, and the scaler will only look at
      *  the lum of one of them.
      */
     switch (rec->fMaskFormat) {
         case SkMask::kLCD16_Format:
         case SkMask::kLCD32_Format: {
             // filter down the luminance color to a finite number of bits
             SkColor color = rec->getLuminanceColor();
@@ skipping 15 matching lines @@
             // reduce to our finite number of bits
             color = SkColorSetRGB(lum, lum, lum);
             rec->setLuminanceColor(SkMaskGamma::CanonicalColor(color));
             break;
         }
         case SkMask::kBW_Format:
             // No need to differentiate gamma if we're BW
             rec->ignorePreBlend();
             break;
     }
+
+    /**
+     *  If we're using distance fields we need to reset the rec to default values
+     */
+    if (paint.isDistanceFieldTextTEMP()) {
+        rec->ignorePreBlend();
+
+        rec->fFlags |= SkScalerContext::kSubpixelPositioning_Flag;
+        rec->fFlags &= ~SkScalerContext::kForceAutohinting_Flag;

[reed1, 2014/05/28 19:45:17]

other than preblend, this rest of this change seems unrelated to gamma. How were
we working before w/o wacking all of these flags?

[jvanverth1, 2014/05/29 18:53:49]

This was done in GrDistanceFieldTextContext::init(), by clearing the flags in
the local copy of SkPaint before getting the SkGlyphCache. I think I could do
that and back up the parameters I need from the SkPaint and DeviceProperties
(the current color, the gamma) if that seems better.

+
+        if (SkMask::kLCD16_Format == rec->fMaskFormat ||
+            SkMask::kLCD32_Format == rec->fMaskFormat) {
+            rec->fMaskFormat = SkMask::kA8_Format;
+        }
+        rec->setHinting(SkPaint::kNo_Hinting);
+    }
+
 }
 
 #define MIN_SIZE_FOR_EFFECT_BUFFER  1024
 
 #ifdef SK_DEBUG
     #define TEST_DESC
 #endif
 
 /*
  *  ignoreGamma tells us that the caller just wants metrics that are unaffected
@@ skipping 145 matching lines @@
  */
 //static
 SkMaskGamma::PreBlend SkScalerContext::GetMaskPreBlend(const SkScalerContext::Rec& rec) {
     SkAutoMutexAcquire ama(gMaskGammaCacheMutex);
     const SkMaskGamma& maskGamma = cachedMaskGamma(rec.getContrast(),
                                                    rec.getPaintGamma(),
                                                    rec.getDeviceGamma());
     return maskGamma.preBlend(rec.getLuminanceColor());
 }
 
+void* SkScalerContext::getGammaLUTData(int& width, int& height, SkScalar contrast,

[reed1, 2014/05/28 19:45:17]

style again: use pointers for out-params

[jvanverth1, 2014/05/29 18:53:49]

Done.

+                                       SkScalar paintGamma, SkScalar deviceGamma) {
+    SkAutoMutexAcquire ama(gMaskGammaCacheMutex);
+    const SkMaskGamma& maskGamma = cachedMaskGamma(contrast,
+                                                   paintGamma,
+                                                   deviceGamma);
+    const uint8_t* gammaTables = maskGamma.getGammaTables(width, height);
+    size_t size = width*height*sizeof(uint8_t);
+    void* data = SkNEW_ARRAY(uint8_t, size);
+    memcpy(data, gammaTables, size);
+
+    return data;
+}
+
+
 ///////////////////////////////////////////////////////////////////////////////
 
 #include "SkStream.h"
 
 static uintptr_t asint(const void* p) {
     return reinterpret_cast<uintptr_t>(p);
 }
 
 union Scalar32 {
     SkScalar    fScalar;
@@ skipping 747 matching lines @@
     }
 #ifdef SK_BUILD_FOR_ANDROID
     if (dirty & kPaintOptionsAndroid_DirtyBit) {
         SkPaintOptionsAndroid options;
         options.unflatten(buffer);
         paint->setPaintOptionsAndroid(options);
     }
 #endif
     SkASSERT(dirty == paint->fDirtyBits);
 }