ui/gfx: split out code that depends on paint

ui/gfx/skia_paint_util.cc

Index: ui/gfx/skia_paint_util.cc
diff --git a/ui/gfx/skia_paint_util.cc b/ui/gfx/skia_paint_util.cc
new file mode 100644
index 0000000000000000000000000000000000000000..fbac6636479fab84e27de8b188ae198b7dc55620
--- /dev/null
+++ b/ui/gfx/skia_paint_util.cc
@@ -0,0 +1,136 @@
+// Copyright (c) 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "ui/gfx/skia_paint_util.h"
+
+#include "third_party/skia/include/core/SkColorFilter.h"
+#include "third_party/skia/include/effects/SkBlurMaskFilter.h"
+#include "third_party/skia/include/effects/SkGradientShader.h"
+#include "third_party/skia/include/effects/SkLayerDrawLooper.h"
+#include "ui/gfx/image/image_skia_rep.h"
+
+namespace gfx {
+
+sk_sp<SkShader> CreateImageRepShader(const gfx::ImageSkiaRep& image_rep,
+                                     SkShader::TileMode tile_mode,
+                                     const SkMatrix& local_matrix) {
+  return CreateImageRepShaderForScale(image_rep, tile_mode, local_matrix,
+                                      image_rep.scale());
+}
+
+sk_sp<SkShader> CreateImageRepShaderForScale(const gfx::ImageSkiaRep& image_rep,
+                                             SkShader::TileMode tile_mode,
+                                             const SkMatrix& local_matrix,
+                                             SkScalar scale) {
+  // Unscale matrix by |scale| such that the bitmap is drawn at the
+  // correct density.
+  // Convert skew and translation to pixel coordinates.
+  // Thus, for |bitmap_scale| = 2:
+  //   x scale = 2, x translation = 1 DIP,
+  // should be converted to
+  //   x scale = 1, x translation = 2 pixels.
+  SkMatrix shader_scale = local_matrix;
+  shader_scale.preScale(scale, scale);
+  shader_scale.setScaleX(local_matrix.getScaleX() / scale);
+  shader_scale.setScaleY(local_matrix.getScaleY() / scale);
+
+  return SkShader::MakeBitmapShader(image_rep.sk_bitmap(), tile_mode, tile_mode,
+                                    &shader_scale);
+}
+
+sk_sp<SkShader> CreateGradientShader(int start_point,
+                                     int end_point,
+                                     SkColor start_color,
+                                     SkColor end_color) {
+  SkColor grad_colors[2] = {start_color, end_color};
+  SkPoint grad_points[2];
+  grad_points[0].iset(0, start_point);
+  grad_points[1].iset(0, end_point);
+
+  return SkGradientShader::MakeLinear(grad_points, grad_colors, NULL, 2,
+                                      SkShader::kClamp_TileMode);
+}
+
+// TODO(estade): remove. Only exists to support legacy CreateShadowDrawLooper.
+static SkScalar DeprecatedRadiusToSigma(double radius) {
+  // This captures historically what skia did under the hood. Now skia accepts
+  // sigma, not radius, so we perform the conversion.
+  return radius > 0 ? SkDoubleToScalar(0.57735f * radius + 0.5) : 0;
+}
+
+// This is copied from
+// third_party/WebKit/Source/platform/graphics/skia/SkiaUtils.h
+static SkScalar RadiusToSigma(double radius) {
+  return radius > 0 ? SkDoubleToScalar(0.288675f * radius + 0.5f) : 0;
+}
+
+sk_sp<SkDrawLooper> CreateShadowDrawLooper(
+    const std::vector<ShadowValue>& shadows) {
+  if (shadows.empty())
+    return nullptr;
+
+  SkLayerDrawLooper::Builder looper_builder;
+
+  looper_builder.addLayer();  // top layer of the original.
+
+  SkLayerDrawLooper::LayerInfo layer_info;
+  layer_info.fPaintBits |= SkLayerDrawLooper::kMaskFilter_Bit;
+  layer_info.fPaintBits |= SkLayerDrawLooper::kColorFilter_Bit;
+  layer_info.fColorMode = SkBlendMode::kSrc;
+
+  for (size_t i = 0; i < shadows.size(); ++i) {
+    const ShadowValue& shadow = shadows[i];
+
+    layer_info.fOffset.set(SkIntToScalar(shadow.x()),
+                           SkIntToScalar(shadow.y()));
+
+    SkPaint* paint = looper_builder.addLayer(layer_info);
+    // SkBlurMaskFilter's blur radius defines the range to extend the blur from
+    // original mask, which is half of blur amount as defined in ShadowValue.
+    // Note that because this function uses DeprecatedRadiusToSigma, it actually
+    // creates a draw looper with roughly twice the desired blur.
+    paint->setMaskFilter(SkBlurMaskFilter::Make(
+        kNormal_SkBlurStyle, DeprecatedRadiusToSigma(shadow.blur() / 2),
+        SkBlurMaskFilter::kHighQuality_BlurFlag));
+    paint->setColorFilter(
+        SkColorFilter::MakeModeFilter(shadow.color(), SkBlendMode::kSrcIn));
+  }
+
+  return looper_builder.detach();
+}
+
+sk_sp<SkDrawLooper> CreateShadowDrawLooperCorrectBlur(
+    const std::vector<ShadowValue>& shadows) {
+  if (shadows.empty())
+    return nullptr;
+
+  SkLayerDrawLooper::Builder looper_builder;
+
+  looper_builder.addLayer();  // top layer of the original.
+
+  SkLayerDrawLooper::LayerInfo layer_info;
+  layer_info.fPaintBits |= SkLayerDrawLooper::kMaskFilter_Bit;
+  layer_info.fPaintBits |= SkLayerDrawLooper::kColorFilter_Bit;
+  layer_info.fColorMode = SkBlendMode::kSrc;
+
+  for (size_t i = 0; i < shadows.size(); ++i) {
+    const ShadowValue& shadow = shadows[i];
+
+    layer_info.fOffset.set(SkIntToScalar(shadow.x()),
+                           SkIntToScalar(shadow.y()));
+
+    SkPaint* paint = looper_builder.addLayer(layer_info);
+    // SkBlurMaskFilter's blur radius defines the range to extend the blur from
+    // original mask, which is half of blur amount as defined in ShadowValue.
+    paint->setMaskFilter(SkBlurMaskFilter::Make(
+        kNormal_SkBlurStyle, RadiusToSigma(shadow.blur() / 2),
+        SkBlurMaskFilter::kHighQuality_BlurFlag));
+    paint->setColorFilter(
+        SkColorFilter::MakeModeFilter(shadow.color(), SkBlendMode::kSrcIn));
+  }
+
+  return looper_builder.detach();
+}
+
+}  // namespace gfx