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 #include "SkRect.h"
12
13 enum SubsetType {
14 kFullyInside_SubsetType,
15 kPartiallyInside_SubsetType,
16 kOutside_SubsetType,
17 };
18
19 /*
20 * Corrects image subset offsets and dimensions in order to perform a valid decode.
21 * Also indicates if the image subset should be placed at an offset within the
22 * output bitmap.
23 *
24 * Values of output variables are undefined if the SubsetType is kInvalid.
25 *
26 * @param imageDims Original image dimensions.
27 * @param subset As input, the subset that the client requested.
28 * As output, the image subset that we will decode.
29 * @param outX The left offset of the image subset within the output bitmap.
30 * @param outY The top offset of the image subset within the output bitmap.
31 *
32 * @return An indication of how the subset is contained in the image.
33 * If the return value is kInvalid, values of output variables are undefined.
34 */
adjust_subset_rect(const SkISize & imageDims,SkIRect * subset,int * outX,int * outY)35 inline SubsetType adjust_subset_rect(const SkISize& imageDims, SkIRect* subset, int* outX,
36 int* outY) {
37 // These must be at least zero, we can't start decoding the image at a negative coordinate.
38 int left = SkTMax(0, subset->fLeft);
39 int top = SkTMax(0, subset->fTop);
40
41 // If input offsets are less than zero, we decode to an offset location in the output bitmap.
42 *outX = left - subset->fLeft;
43 *outY = top - subset->fTop;
44
45 // Make sure we don't decode pixels past the edge of the image or past the edge of the subset.
46 int width = SkTMin(imageDims.width() - left, subset->width() - *outX);
47 int height = SkTMin(imageDims.height() - top, subset->height() - *outY);
48 if (width <= 0 || height <= 0) {
49 return SubsetType::kOutside_SubsetType;
50 }
51
52 subset->setXYWH(left, top, width, height);
53 if ((*outX != 0) || (*outY != 0) || (width != subset->width()) ||
54 (height != subset->height())) {
55 return SubsetType::kPartiallyInside_SubsetType;
56 }
57
58 return SubsetType::kFullyInside_SubsetType;
59 }
60
61 #endif // SkBitmapRegionDecoderPriv_DEFINED
62