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 #ifndef SkBitmapRegionDecoderPriv_DEFINED
9 #define SkBitmapRegionDecoderPriv_DEFINED
10
11 enum SubsetType {
12 kFullyInside_SubsetType,
13 kPartiallyInside_SubsetType,
14 kOutside_SubsetType,
15 };
16
17 /*
18 * Corrects image subset offsets and dimensions in order to perform a valid decode.
19 * Also indicates if the image subset should be placed at an offset within the
20 * output bitmap.
21 *
22 * Values of output variables are undefined if the SubsetType is kInvalid.
23 *
24 * @param imageDims Original image dimensions.
25 * @param subset As input, the subset that the client requested.
26 * As output, the image subset that we will decode.
27 * @param outX The left offset of the image subset within the output bitmap.
28 * @param outY The top offset of the image subset within the output bitmap.
29 *
30 * @return An indication of how the subset is contained in the image.
31 * If the return value is kInvalid, values of output variables are undefined.
32 */
adjust_subset_rect(const SkISize & imageDims,SkIRect * subset,int * outX,int * outY)33 inline SubsetType adjust_subset_rect(const SkISize& imageDims, SkIRect* subset, int* outX,
34 int* outY) {
35 // These must be at least zero, we can't start decoding the image at a negative coordinate.
36 int left = SkTMax(0, subset->fLeft);
37 int top = SkTMax(0, subset->fTop);
38
39 // If input offsets are less than zero, we decode to an offset location in the output bitmap.
40 *outX = left - subset->fLeft;
41 *outY = top - subset->fTop;
42
43 // Make sure we don't decode pixels past the edge of the image or past the edge of the subset.
44 int width = SkTMin(imageDims.width() - left, subset->width() - *outX);
45 int height = SkTMin(imageDims.height() - top, subset->height() - *outY);
46 if (width <= 0 || height <= 0) {
47 return SubsetType::kOutside_SubsetType;
48 }
49
50 subset->setXYWH(left, top, width, height);
51 if ((*outX != 0) || (*outY != 0) || (width != subset->width()) ||
52 (height != subset->height())) {
53 return SubsetType::kPartiallyInside_SubsetType;
54 }
55
56 return SubsetType::kFullyInside_SubsetType;
57 }
58
59 #endif // SkBitmapRegionDecoderPriv_DEFINED
60