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 "SkCodecPriv.h"
9 #include "SkMasks.h"
10 #include "SkTypes.h"
11
12 /*
13 *
14 * Used to convert 1-7 bit color components into 8-bit color components
15 *
16 */
17 const static uint8_t n_bit_to_8_bit_lookup_table[] = {
18 // 1 bit
19 0, 255,
20 // 2 bits
21 0, 85, 170, 255,
22 // 3 bits
23 0, 36, 73, 109, 146, 182, 219, 255,
24 // 4 bits
25 0, 17, 34, 51, 68, 85, 102, 119, 136, 153, 170, 187, 204, 221, 238, 255,
26 // 5 bits
27 0, 8, 16, 25, 33, 41, 49, 58, 66, 74, 82, 90, 99, 107, 115, 123, 132, 140,
28 148, 156, 165, 173, 181, 189, 197, 206, 214, 222, 230, 239, 247, 255,
29 // 6 bits
30 0, 4, 8, 12, 16, 20, 24, 28, 32, 36, 40, 45, 49, 53, 57, 61, 65, 69, 73,
31 77, 81, 85, 89, 93, 97, 101, 105, 109, 113, 117, 121, 125, 130, 134, 138,
32 142, 146, 150, 154, 158, 162, 166, 170, 174, 178, 182, 186, 190, 194, 198,
33 202, 206, 210, 215, 219, 223, 227, 231, 235, 239, 243, 247, 251, 255,
34 // 7 bits
35 0, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28, 30, 32, 34, 36, 38,
36 40, 42, 44, 46, 48, 50, 52, 54, 56, 58, 60, 62, 64, 66, 68, 70, 72, 74, 76,
37 78, 80, 82, 84, 86, 88, 90, 92, 94, 96, 98, 100, 102, 104, 106, 108, 110,
38 112, 114, 116, 118, 120, 122, 124, 126, 129, 131, 133, 135, 137, 139, 141,
39 143, 145, 147, 149, 151, 153, 155, 157, 159, 161, 163, 165, 167, 169, 171,
40 173, 175, 177, 179, 181, 183, 185, 187, 189, 191, 193, 195, 197, 199, 201,
41 203, 205, 207, 209, 211, 213, 215, 217, 219, 221, 223, 225, 227, 229, 231,
42 233, 235, 237, 239, 241, 243, 245, 247, 249, 251, 253, 255
43 };
44
45 /*
46 *
47 * Convert an n bit component to an 8-bit component
48 *
49 */
convert_to_8(uint8_t component,uint32_t n)50 static uint8_t convert_to_8(uint8_t component, uint32_t n) {
51 if (0 == n) {
52 return 0;
53 } else if (8 > n) {
54 return n_bit_to_8_bit_lookup_table[(1 << n) - 2 + component];
55 } else {
56 SkASSERT(8 == n);
57 return component;
58 }
59 }
60
get_comp(uint32_t pixel,uint32_t mask,uint32_t shift,uint32_t size)61 static uint8_t get_comp(uint32_t pixel, uint32_t mask, uint32_t shift,
62 uint32_t size) {
63 return convert_to_8((pixel & mask) >> shift, size);
64 }
65
66 /*
67 *
68 * Get a color component
69 *
70 */
getRed(uint32_t pixel) const71 uint8_t SkMasks::getRed(uint32_t pixel) const {
72 return get_comp(pixel, fRed.mask, fRed.shift, fRed.size);
73 }
getGreen(uint32_t pixel) const74 uint8_t SkMasks::getGreen(uint32_t pixel) const {
75 return get_comp(pixel, fGreen.mask, fGreen.shift, fGreen.size);
76 }
getBlue(uint32_t pixel) const77 uint8_t SkMasks::getBlue(uint32_t pixel) const {
78 return get_comp(pixel, fBlue.mask, fBlue.shift, fBlue.size);
79 }
getAlpha(uint32_t pixel) const80 uint8_t SkMasks::getAlpha(uint32_t pixel) const {
81 return get_comp(pixel, fAlpha.mask, fAlpha.shift, fAlpha.size);
82 }
83
84 /*
85 *
86 * Process an input mask to obtain the necessary information
87 *
88 */
process_mask(uint32_t mask,uint32_t bpp)89 const SkMasks::MaskInfo process_mask(uint32_t mask, uint32_t bpp) {
90 // Determine properties of the mask
91 uint32_t tempMask = mask;
92 uint32_t shift = 0;
93 uint32_t size = 0;
94 if (tempMask != 0) {
95 // Count trailing zeros on masks
96 for (; (tempMask & 1) == 0; tempMask >>= 1) {
97 shift++;
98 }
99 // Count the size of the mask
100 for (; tempMask & 1; tempMask >>= 1) {
101 size++;
102 }
103 // Verify that the mask is continuous
104 if (tempMask) {
105 SkCodecPrintf("Warning: Bit mask is not continuous.\n");
106 // Finish processing the mask
107 for (; tempMask; tempMask >>= 1) {
108 size++;
109 }
110 }
111 // Truncate masks greater than 8 bits
112 if (size > 8) {
113 shift += size - 8;
114 size = 8;
115 mask &= 0xFF << shift;
116 }
117 }
118
119 // Save the calculated values
120 const SkMasks::MaskInfo info = { mask, shift, size };
121 return info;
122 }
123
124 /*
125 *
126 * Create the masks object
127 *
128 */
CreateMasks(InputMasks masks,uint32_t bitsPerPixel)129 SkMasks* SkMasks::CreateMasks(InputMasks masks, uint32_t bitsPerPixel) {
130 // Trim the input masks according to bitsPerPixel
131 if (bitsPerPixel < 32) {
132 masks.red &= (1 << bitsPerPixel) - 1;
133 masks.green &= (1 << bitsPerPixel) - 1;
134 masks.blue &= (1 << bitsPerPixel) - 1;
135 masks.alpha &= (1 << bitsPerPixel) - 1;
136 }
137
138 // Check that masks do not overlap
139 if (((masks.red & masks.green) | (masks.red & masks.blue) |
140 (masks.red & masks.alpha) | (masks.green & masks.blue) |
141 (masks.green & masks.alpha) | (masks.blue & masks.alpha)) != 0) {
142 return nullptr;
143 }
144
145 // Collect information about the masks
146 const MaskInfo red = process_mask(masks.red, bitsPerPixel);
147 const MaskInfo green = process_mask(masks.green, bitsPerPixel);
148 const MaskInfo blue = process_mask(masks.blue, bitsPerPixel);
149 const MaskInfo alpha = process_mask(masks.alpha, bitsPerPixel);
150
151 return new SkMasks(red, green, blue, alpha);
152 }
153
154
SkMasks(const MaskInfo & red,const MaskInfo & green,const MaskInfo & blue,const MaskInfo & alpha)155 SkMasks::SkMasks(const MaskInfo& red, const MaskInfo& green,
156 const MaskInfo& blue, const MaskInfo& alpha)
157 : fRed(red)
158 , fGreen(green)
159 , fBlue(blue)
160 , fAlpha(alpha)
161 {}
162