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  */
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