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      1 /*
      2  * Copyright 2013 Google Inc.
      3  *
      4  * Use of this source code is governed by a BSD-style license that can be
      5  * found in the LICENSE file.
      6  */
      7 
      8 #include "SkBitmap.h"
      9 #include "SkColorFilter.h"
     10 #include "SkPaintPriv.h"
     11 #include "SkImage.h"
     12 #include "SkPaint.h"
     13 #include "SkShaderBase.h"
     14 #include "SkXfermodePriv.h"
     15 
     16 static bool changes_alpha(const SkPaint& paint) {
     17     SkColorFilter* cf = paint.getColorFilter();
     18     return cf && !(cf->getFlags() & SkColorFilter::kAlphaUnchanged_Flag);
     19 }
     20 
     21 bool SkPaintPriv::Overwrites(const SkPaint* paint, ShaderOverrideOpacity overrideOpacity) {
     22     if (!paint) {
     23         // No paint means we default to SRC_OVER, so we overwrite iff our shader-override
     24         // is opaque, or we don't have one.
     25         return overrideOpacity != kNotOpaque_ShaderOverrideOpacity;
     26     }
     27 
     28     SkXfermode::SrcColorOpacity opacityType = SkXfermode::kUnknown_SrcColorOpacity;
     29 
     30     if (!changes_alpha(*paint)) {
     31         const unsigned paintAlpha = paint->getAlpha();
     32         if (0xff == paintAlpha && overrideOpacity != kNotOpaque_ShaderOverrideOpacity &&
     33             (!paint->getShader() || paint->getShader()->isOpaque()))
     34         {
     35             opacityType = SkXfermode::kOpaque_SrcColorOpacity;
     36         } else if (0 == paintAlpha) {
     37             if (overrideOpacity == kNone_ShaderOverrideOpacity && !paint->getShader()) {
     38                 opacityType = SkXfermode::kTransparentBlack_SrcColorOpacity;
     39             } else {
     40                 opacityType = SkXfermode::kTransparentAlpha_SrcColorOpacity;
     41             }
     42         }
     43     }
     44 
     45     return SkXfermode::IsOpaque(paint->getBlendMode(), opacityType);
     46 }
     47 
     48 bool SkPaintPriv::Overwrites(const SkBitmap& bitmap, const SkPaint* paint) {
     49     return Overwrites(paint, bitmap.isOpaque() ? kOpaque_ShaderOverrideOpacity
     50                                                : kNotOpaque_ShaderOverrideOpacity);
     51 }
     52 
     53 bool SkPaintPriv::Overwrites(const SkImage* image, const SkPaint* paint) {
     54     return Overwrites(paint, image->isOpaque() ? kOpaque_ShaderOverrideOpacity
     55                                                : kNotOpaque_ShaderOverrideOpacity);
     56 }
     57 
     58 void SkPaintPriv::ScaleFontMetrics(SkPaint::FontMetrics* metrics, SkScalar scale) {
     59     metrics->fTop *= scale;
     60     metrics->fAscent *= scale;
     61     metrics->fDescent *= scale;
     62     metrics->fBottom *= scale;
     63     metrics->fLeading *= scale;
     64     metrics->fAvgCharWidth *= scale;
     65     metrics->fXMin *= scale;
     66     metrics->fXMax *= scale;
     67     metrics->fXHeight *= scale;
     68     metrics->fUnderlineThickness *= scale;
     69     metrics->fUnderlinePosition *= scale;
     70 }
     71 
     72 bool SkPaintPriv::ShouldDither(const SkPaint& p, SkColorType dstCT) {
     73     // The paint dither flag can veto.
     74     if (!p.isDither()) {
     75         return false;
     76     }
     77 
     78     // We always dither 565 or 4444 when requested.
     79     if (dstCT == kRGB_565_SkColorType || dstCT == kARGB_4444_SkColorType) {
     80         return true;
     81     }
     82 
     83     // Otherwise, dither is only needed for non-const paints.
     84     return p.getImageFilter() || p.getMaskFilter()
     85         || !p.getShader() || !as_SB(p.getShader())->isConstant();
     86 }
     87