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1 /* | |
2 * Copyright 2015 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 "SkBitmapRegionCanvas.h" | |
9 #include "SkCanvas.h" | |
10 #include "SkScanlineDecoder.h" | |
11 | |
12 SkBitmapRegionCanvas::SkBitmapRegionCanvas(SkScanlineDecoder* decoder) | |
13 : INHERITED(decoder->getInfo().width(), decoder->getInfo().height()) | |
14 , fDecoder(decoder) | |
15 {} | |
16 | |
17 /* | |
18 * Adjusts the image subset dimensions to safely fit within the original image, | |
19 * and to safely fit within the requested region size. | |
20 */ | |
21 static int get_safe_subset_dimension(int imageOffset, int imageDim, int regionOf fset, | |
scroggo
2015/09/03 20:07:41
These names are pretty opaque to me. They describe
msarett
2015/09/03 22:10:30
I'll add comments, I was hoping the names would ma
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22 int regionDim) { | |
23 int safeImageDim = imageDim - imageOffset; | |
24 int safeRegionDim = regionDim - regionOffset; | |
25 return SkTMin(safeImageDim, safeRegionDim); | |
26 } | |
27 | |
28 static int get_scaled_dimension(int dimension, int sampleSize) { | |
29 return SkTMax(1, dimension / sampleSize); | |
scroggo
2015/09/03 20:07:41
It seems like this is logically the same as SkScal
msarett
2015/09/03 22:10:30
Yeah I tried to share it in SkCodecPriv.h but that
scroggo
2015/09/04 17:55:06
Ah, because this is in utils? maybe declare it as
msarett
2015/09/04 18:54:10
I'll go with the original implementation in SkScal
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30 } | |
31 | |
32 /* | |
33 * This has several key differences from the Android version: | |
34 * Returns a Skia bitmap instead of an Android bitmap. | |
35 * Android version attempts to reuse a recycled bitmap. | |
36 */ | |
37 SkBitmap* SkBitmapRegionCanvas::decodeRegion(int input_x, int input_y, | |
38 int input_w, int input_h, | |
39 int sampleSize, | |
40 SkColorType dstColorType) { | |
41 // Reject color types not supported by this method | |
42 if (kIndex_8_SkColorType == dstColorType || kGray_8_SkColorType == dstColorT ype) { | |
43 SkDebugf("Error: Color type not supported.\n"); | |
44 return nullptr; | |
45 } | |
46 | |
47 // Correct the output region if necessary | |
48 const int left = SkTMax(0, input_x); | |
49 const int leftOffset = left - input_x; | |
50 const int top = SkTMax(0, input_y); | |
51 const int topOffset = top - input_y; | |
52 const int width = get_safe_subset_dimension(left, this->width(), leftOffset, input_w); | |
53 const int height = get_safe_subset_dimension(top, this->height(), topOffset, input_h); | |
54 if (width <= 0 || height <= 0) { | |
55 SkDebugf("Error: Region must intersect part of the image.\n"); | |
56 return nullptr; | |
57 } | |
58 | |
59 // Create the image info for the decode | |
60 SkAlphaType dstAlphaType = fDecoder->getInfo().alphaType(); | |
61 if (kUnpremul_SkAlphaType == dstAlphaType) { | |
62 dstAlphaType = kPremul_SkAlphaType; | |
63 } | |
64 SkImageInfo decodeInfo = SkImageInfo::Make(this->width(), this->height(), | |
65 dstColorType, dstAlphaType); | |
66 | |
67 // Start the scanline decoder | |
68 SkCodec::Result r = fDecoder->start(decodeInfo); | |
69 if (SkCodec::kSuccess != r) { | |
70 SkDebugf("Error: Could not start scanline decoder.\n"); | |
71 return nullptr; | |
72 } | |
73 | |
74 // Allocate a bitmap for the unscaled decode | |
75 SkBitmap tmp; | |
76 SkImageInfo tmpInfo = decodeInfo.makeWH(this->width(), height); | |
77 if (!tmp.tryAllocPixels(tmpInfo)) { | |
78 SkDebugf("Error: Could not allocate pixels.\n"); | |
79 return nullptr; | |
80 } | |
81 | |
82 // Skip the unneeded rows | |
83 if (SkCodec::kSuccess != fDecoder->skipScanlines(top)) { | |
84 SkDebugf("Error: Failed to skip scanlines.\n"); | |
85 return nullptr; | |
86 } | |
87 | |
88 // Decode the necessary rows | |
89 SkCodec::Result result = fDecoder->getScanlines(tmp.getAddr(0, 0), height, | |
90 tmp.rowBytes()); | |
91 switch (result) { | |
92 case SkCodec::kSuccess: | |
93 case SkCodec::kIncompleteInput: | |
94 break; | |
95 default: | |
96 SkDebugf("Error: Failed to get scanlines.\n"); | |
97 return nullptr; | |
98 } | |
99 | |
100 // Calculate the size of the output | |
101 const int outWidth = get_scaled_dimension(input_w, sampleSize); | |
102 const int outHeight = get_scaled_dimension(input_h, sampleSize); | |
103 | |
104 // Initialize the destination bitmap | |
105 SkAutoTDelete<SkBitmap> bitmap(new SkBitmap()); | |
106 SkImageInfo dstInfo = decodeInfo.makeWH(outWidth, outHeight); | |
107 if (!bitmap->tryAllocPixels(dstInfo)) { | |
108 SkDebugf("Error: Could not allocate pixels.\n"); | |
109 return nullptr; | |
110 } | |
111 | |
112 // Zero the bitmap if the region is not completely within the image. | |
113 // TODO (msarett): Can we make this faster by implementing it to only | |
114 // zero parts of the image that we won't overwrite with | |
115 // pixels? | |
116 // TODO (msarett): This could be skipped if memory is zero initialized. | |
117 // This would matter if this code is moved to Android and | |
118 // uses Android bitmaps. | |
119 if (0 != leftOffset || 0 != topOffset || | |
120 input_x + input_w > this->width() || | |
121 input_y + input_h > this->height()) { | |
122 bitmap->eraseColor(0); | |
123 } | |
124 | |
125 // Use a canvas to crop and scale to the destination bitmap | |
126 SkCanvas canvas(*bitmap); | |
127 SkRect src = SkRect::MakeXYWH(left, 0, width, height); | |
128 SkRect dst = SkRect::MakeXYWH(leftOffset / sampleSize, topOffset / sampleSiz e, | |
129 get_scaled_dimension(width, sampleSize), get_scaled_dimension(height , sampleSize)); | |
130 SkPaint paint; | |
131 // Overwrite the dst with the src pixels | |
132 paint.setXfermodeMode(SkXfermode::kSrc_Mode); | |
133 // TODO (msarett): Test multiple filter qualities. kNone is the default. | |
134 canvas.drawBitmapRect(tmp, src, dst, &paint); | |
135 | |
136 return bitmap.detach(); | |
137 } | |
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