1 /*
2 * Copyright 2023 Google LLC
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 * This file contains implementations of SkPixmap methods which require the CPU backend.
8 */
9
10 #include "include/core/SkAlphaType.h"
11 #include "include/core/SkBitmap.h"
12 #include "include/core/SkBlendMode.h"
13 #include "include/core/SkCanvas.h"
14 #include "include/core/SkImageInfo.h"
15 #include "include/core/SkMatrix.h"
16 #include "include/core/SkPaint.h"
17 #include "include/core/SkPixmap.h"
18 #include "include/core/SkRect.h"
19 #include "include/core/SkRefCnt.h"
20 #include "include/core/SkShader.h"
21 #include "include/core/SkSurface.h"
22 #include "include/core/SkTileMode.h"
23 #include "src/shaders/SkImageShader.h"
24
25 #include <utility>
26
27 struct SkSamplingOptions;
28
scalePixels(const SkPixmap & actualDst,const SkSamplingOptions & sampling) const29 bool SkPixmap::scalePixels(const SkPixmap& actualDst, const SkSamplingOptions& sampling) const {
30 // We may need to tweak how we interpret these just a little below, so we make copies.
31 SkPixmap src = *this,
32 dst = actualDst;
33
34 // Can't do anthing with empty src or dst
35 if (src.width() <= 0 || src.height() <= 0 ||
36 dst.width() <= 0 || dst.height() <= 0) {
37 return false;
38 }
39
40 // no scaling involved?
41 if (src.width() == dst.width() && src.height() == dst.height()) {
42 return src.readPixels(dst);
43 }
44
45 // If src and dst are both unpremul, we'll fake the source out to appear as if premul,
46 // and mark the destination as opaque. This odd combination allows us to scale unpremul
47 // pixels without ever premultiplying them (perhaps losing information in the color channels).
48 // This is an idiosyncratic feature of scalePixels(), and is tested by scalepixels_unpremul GM.
49 bool clampAsIfUnpremul = false;
50 if (src.alphaType() == kUnpremul_SkAlphaType &&
51 dst.alphaType() == kUnpremul_SkAlphaType) {
52 src.reset(src.info().makeAlphaType(kPremul_SkAlphaType), src.addr(), src.rowBytes());
53 dst.reset(dst.info().makeAlphaType(kOpaque_SkAlphaType), dst.addr(), dst.rowBytes());
54
55 // We'll need to tell the image shader to clamp to [0,1] instead of the
56 // usual [0,a] when using a bicubic scaling (kHigh_SkFilterQuality).
57 clampAsIfUnpremul = true;
58 }
59
60 SkBitmap bitmap;
61 if (!bitmap.installPixels(src)) {
62 return false;
63 }
64 bitmap.setImmutable(); // Don't copy when we create an image.
65
66 SkMatrix scale = SkMatrix::RectToRect(SkRect::Make(src.bounds()), SkRect::Make(dst.bounds()));
67
68 sk_sp<SkShader> shader = SkImageShader::Make(bitmap.asImage(),
69 SkTileMode::kClamp,
70 SkTileMode::kClamp,
71 sampling,
72 &scale,
73 clampAsIfUnpremul);
74
75 sk_sp<SkSurface> surface =
76 SkSurfaces::WrapPixels(dst.info(), dst.writable_addr(), dst.rowBytes());
77 if (!shader || !surface) {
78 return false;
79 }
80
81 SkPaint paint;
82 paint.setBlendMode(SkBlendMode::kSrc);
83 paint.setShader(std::move(shader));
84 surface->getCanvas()->drawPaint(paint);
85 return true;
86 }
87