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 */
17const 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 */
50static 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
61static 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 */
71uint8_t SkMasks::getRed(uint32_t pixel) const {
72    return get_comp(pixel, fRed.mask, fRed.shift, fRed.size);
73}
74uint8_t SkMasks::getGreen(uint32_t pixel) const {
75    return get_comp(pixel, fGreen.mask, fGreen.shift, fGreen.size);
76}
77uint8_t SkMasks::getBlue(uint32_t pixel) const {
78    return get_comp(pixel, fBlue.mask, fBlue.shift, fBlue.size);
79}
80uint8_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 */
89const 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 */
129SkMasks* 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
155SkMasks::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