Revert "Fix dithering on drawImage[Rect] calls"

This reverts commit 1024148.

Reason for revert: Speculative revert for b/220676062

Original change's description:
> Fix dithering on drawImage[Rect] calls
>
> Bug: skia:12516
> Change-Id: Ibb68558e0f474143df3c6a5fb0fb3d4881529226
> Reviewed-on: https://skia-review.googlesource.com/c/skia/+/508677
> Reviewed-by: Brian Osman <[email protected]>
> Commit-Queue: Michael Ludwig <[email protected]>

Bug: skia:12516
Change-Id: If496c6be355bbb026ffe478512f8a6334116bb66
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/511806
Commit-Queue: Brian Osman <[email protected]>
Bot-Commit: Rubber Stamper <[email protected]>

gm/image.cpp

@@ -29,7 +29,6 @@
 #include "include/core/SkSurface.h"
 #include "include/core/SkTypeface.h"
 #include "include/core/SkTypes.h"
-#include "include/effects/SkGradientShader.h"
 #include "include/gpu/GrDirectContext.h"
 #include "include/private/SkMalloc.h"
 #include "src/core/SkAutoPixmapStorage.h"
@@ -460,39 +459,3 @@ DEF_SIMPLE_GM_CAN_FAIL(image_subset, canvas, errorMsg, 440, 220) {
     canvas->drawImage(sub, 220+110, 10);
     return skiagm::DrawResult::kOk;
 }
-
-///////////////////////////////////////////////////////////////////////////////////////////////////
-
-DEF_SIMPLE_GM(image_dither, canvas, 800, 800) {
-    // Make a low-res image of a gradient that shows banding if there's no dithering. When up-scaled
-    // bilerp filtering will emphasize the banding unless the image is drawn with dithering.
-    auto gradImage = []() -> sk_sp<SkImage> {
-        SkImageInfo gradImageInfo = SkImageInfo::Make({8, 16}, {SkColorType::kRGBA_8888_SkColorType,
-                                                                SkAlphaType::kPremul_SkAlphaType,
-                                                                nullptr});
-        auto surface = SkSurface::MakeRaster(gradImageInfo);
-
-        SkPoint pts[2] = {{0.f, 0.f},
-                          {(float) 2 * gradImageInfo.width(), (float) gradImageInfo.height()}};
-        const SkColor colors[] = { 0xFF555555, 0xFF444444 };
-        SkPaint p;
-        p.setShader(SkGradientShader::MakeLinear(pts, colors, nullptr, 2, SkTileMode::kClamp));
-        surface->getCanvas()->drawPaint(p);
-        return surface->makeImageSnapshot();
-    }();
-
-    SkRect imageBounds = SkRect::MakeIWH(gradImage->width(), gradImage->height());
-
-    canvas->scale(50, 50);
-
-    // 1st image definitely goes through general shader paths so should have dithering
-    SkPaint p;
-    p.setShader(gradImage->makeShader(SkSamplingOptions{SkFilterMode::kLinear}));
-    p.setDither(true);
-    canvas->drawRect(imageBounds, p);
-
-    // 2nd image goes through draw-image fast paths, but dithering should be detected
-    p.setShader(nullptr);
-    canvas->translate(imageBounds.width(), 0.f);
-    canvas->drawImage(gradImage, 0.f, 0.f, SkSamplingOptions{SkFilterMode::kLinear}, &p);
-}

src/core/SkMatrix.cpp

@@ -1639,9 +1639,7 @@ bool SkTreatAsSprite(const SkMatrix& mat, const SkISize& size, const SkSamplingO
     if (!SkSamplingPriv::NoChangeWithIdentityMatrix(sampling)) {
         return false;
     }
-    if (paint.isDither()) {
-        return false;
-    }
+
     // Our path aa is 2-bits, and our rect aa is 8, so we could use 8,
     // but in practice 4 seems enough (still looks smooth) and allows
     // more slightly fractional cases to fall into the fast (sprite) case.

src/core/SkPaintPriv.cpp

@@ -50,7 +50,7 @@ bool SkPaintPriv::Overwrites(const SkPaint* paint, ShaderOverrideOpacity overrid
     return SkXfermode::IsOpaque(bm.value(), opacityType);
 }
 
-bool SkPaintPriv::ShouldDither(const SkPaint& p, SkColorType dstCT, bool shaderOverride) {
+bool SkPaintPriv::ShouldDither(const SkPaint& p, SkColorType dstCT) {
     // The paint dither flag can veto.
     if (!p.isDither()) {
         return false;
@@ -63,8 +63,7 @@ bool SkPaintPriv::ShouldDither(const SkPaint& p, SkColorType dstCT, bool shaderO
 
     // Otherwise, dither is only needed for non-const paints.
     return p.getImageFilter() || p.getMaskFilter() ||
-           (p.getShader() && !as_SB(p.getShader())->isConstant()) ||
-           shaderOverride;
+           (p.getShader() && !as_SB(p.getShader())->isConstant());
 }
 
 // return true if the paint is just a single color (i.e. not a shader). If its

src/core/SkPaintPriv.h

@@ -29,7 +29,7 @@ class SkPaintPriv {
      */
     static bool Overwrites(const SkPaint* paint, ShaderOverrideOpacity);
 
-    static bool ShouldDither(const SkPaint&, SkColorType, bool shaderOverride=false);
+    static bool ShouldDither(const SkPaint&, SkColorType);
 
     /*
      * The luminance color is used to determine which Gamma Canonical color to map to.  This is

src/gpu/SkGr.cpp

@@ -548,8 +548,7 @@ static inline bool skpaint_to_grpaint_impl(
 
 #ifndef SK_IGNORE_GPU_DITHER
     GrColorType ct = dstColorInfo.colorType();
-    const bool shaderOverride = SkToBool(paintFP);
-    if (SkPaintPriv::ShouldDither(skPaint, GrColorTypeToSkColorType(ct), shaderOverride)) {
+    if (SkPaintPriv::ShouldDither(skPaint, GrColorTypeToSkColorType(ct)) && paintFP != nullptr) {
         float ditherRange = dither_range_for_config(ct);
         paintFP = make_dither_effect(
                 context, std::move(paintFP), ditherRange, context->priv().caps());

src/gpu/v1/Device_drawTexture.cpp

@@ -321,8 +321,8 @@ ImageDrawMode optimize_sample_area(const SkISize& image, const SkRect* origSrcRe
  */
 bool can_use_draw_texture(const SkPaint& paint, bool useCubicResampler, SkMipmapMode mm) {
     return (!paint.getColorFilter() && !paint.getShader() && !paint.getMaskFilter() &&
-            !paint.getImageFilter() && !paint.getBlender() && !paint.isDither() &&
-            !useCubicResampler && mm == SkMipmapMode::kNone);
+            !paint.getImageFilter() && !paint.getBlender() && !useCubicResampler &&
+            mm == SkMipmapMode::kNone);
 }
 
 SkPMColor4f texture_color(SkColor4f paintColor, float entryAlpha, GrColorType srcColorType,