SkCodecPriv.h revision cf3f2347c8933596aeba873d4ece597a9339392f 
1/*
2 * Copyright 2015 The Android Open Source Project
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 SkCodecPriv_DEFINED
9#define SkCodecPriv_DEFINED
10
11#include "SkColorPriv.h"
12#include "SkColorSpaceXform.h"
13#include "SkColorSpaceXformPriv.h"
14#include "SkColorTable.h"
15#include "SkEncodedInfo.h"
16#include "SkImageInfo.h"
17#include "SkTypes.h"
18
19#ifdef SK_PRINT_CODEC_MESSAGES
20    #define SkCodecPrintf SkDebugf
21#else
22    #define SkCodecPrintf(...)
23#endif
24
25// FIXME: Consider sharing with dm, nanbench, and tools.
26static inline float get_scale_from_sample_size(int sampleSize) {
27    return 1.0f / ((float) sampleSize);
28}
29
30static inline bool is_valid_subset(const SkIRect& subset, const SkISize& imageDims) {
31    return SkIRect::MakeSize(imageDims).contains(subset);
32}
33
34/*
35 * returns a scaled dimension based on the original dimension and the sampleSize
36 * NOTE: we round down here for scaled dimension to match the behavior of SkImageDecoder
37 * FIXME: I think we should call this get_sampled_dimension().
38 */
39static inline int get_scaled_dimension(int srcDimension, int sampleSize) {
40    if (sampleSize > srcDimension) {
41        return 1;
42    }
43    return srcDimension / sampleSize;
44}
45
46/*
47 * Returns the first coordinate that we will keep during a scaled decode.
48 * The output can be interpreted as an x-coordinate or a y-coordinate.
49 *
50 * This does not need to be called and is not called when sampleFactor == 1.
51 */
52static inline int get_start_coord(int sampleFactor) { return sampleFactor / 2; };
53
54/*
55 * Given a coordinate in the original image, this returns the corresponding
56 * coordinate in the scaled image.  This function is meaningless if
57 * IsCoordNecessary returns false.
58 * The output can be interpreted as an x-coordinate or a y-coordinate.
59 *
60 * This does not need to be called and is not called when sampleFactor == 1.
61 */
62static inline int get_dst_coord(int srcCoord, int sampleFactor) { return srcCoord / sampleFactor; };
63
64/*
65 * When scaling, we will discard certain y-coordinates (rows) and
66 * x-coordinates (columns).  This function returns true if we should keep the
67 * coordinate and false otherwise.
68 * The inputs may be x-coordinates or y-coordinates.
69 *
70 * This does not need to be called and is not called when sampleFactor == 1.
71 */
72static inline bool is_coord_necessary(int srcCoord, int sampleFactor, int scaledDim) {
73    // Get the first coordinate that we want to keep
74    int startCoord = get_start_coord(sampleFactor);
75
76    // Return false on edge cases
77    if (srcCoord < startCoord || get_dst_coord(srcCoord, sampleFactor) >= scaledDim) {
78        return false;
79    }
80
81    // Every sampleFactor rows are necessary
82    return ((srcCoord - startCoord) % sampleFactor) == 0;
83}
84
85static inline bool valid_alpha(SkAlphaType dstAlpha, SkAlphaType srcAlpha) {
86    if (kUnknown_SkAlphaType == dstAlpha) {
87        return false;
88    }
89
90    if (srcAlpha != dstAlpha) {
91        if (kOpaque_SkAlphaType == srcAlpha) {
92            // If the source is opaque, we can support any.
93            SkCodecPrintf("Warning: an opaque image should be decoded as opaque "
94                          "- it is being decoded as non-opaque, which will draw slower\n");
95            return true;
96        }
97
98        // The source is not opaque
99        switch (dstAlpha) {
100            case kPremul_SkAlphaType:
101            case kUnpremul_SkAlphaType:
102                // The source is not opaque, so either of these is okay
103                break;
104            default:
105                // We cannot decode a non-opaque image to opaque (or unknown)
106                return false;
107        }
108    }
109    return true;
110}
111
112/*
113 * If there is a color table, get a pointer to the colors, otherwise return nullptr
114 */
115static inline const SkPMColor* get_color_ptr(SkColorTable* colorTable) {
116     return nullptr != colorTable ? colorTable->readColors() : nullptr;
117}
118
119/*
120 * Given that the encoded image uses a color table, return the fill value
121 */
122static inline uint64_t get_color_table_fill_value(SkColorType dstColorType, SkAlphaType alphaType,
123        const SkPMColor* colorPtr, uint8_t fillIndex, SkColorSpaceXform* colorXform) {
124    SkASSERT(nullptr != colorPtr);
125    switch (dstColorType) {
126        case kRGBA_8888_SkColorType:
127        case kBGRA_8888_SkColorType:
128            return colorPtr[fillIndex];
129        case kRGB_565_SkColorType:
130            return SkPixel32ToPixel16(colorPtr[fillIndex]);
131        case kIndex_8_SkColorType:
132            return fillIndex;
133        case kRGBA_F16_SkColorType: {
134            SkASSERT(colorXform);
135            uint64_t dstColor;
136            uint32_t srcColor = colorPtr[fillIndex];
137            SkAssertResult(colorXform->apply(select_xform_format(dstColorType), &dstColor,
138                    SkColorSpaceXform::kRGBA_8888_ColorFormat, &srcColor, 1, alphaType));
139            return dstColor;
140        }
141        default:
142            SkASSERT(false);
143            return 0;
144    }
145}
146
147/*
148 *
149 * Copy the codec color table back to the client when kIndex8 color type is requested
150 */
151static inline void copy_color_table(const SkImageInfo& dstInfo, SkColorTable* colorTable,
152        SkPMColor* inputColorPtr, int* inputColorCount) {
153    if (kIndex_8_SkColorType == dstInfo.colorType()) {
154        SkASSERT(nullptr != inputColorPtr);
155        SkASSERT(nullptr != inputColorCount);
156        SkASSERT(nullptr != colorTable);
157        memcpy(inputColorPtr, colorTable->readColors(), *inputColorCount * sizeof(SkPMColor));
158    }
159}
160
161/*
162 * Compute row bytes for an image using pixels per byte
163 */
164static inline size_t compute_row_bytes_ppb(int width, uint32_t pixelsPerByte) {
165    return (width + pixelsPerByte - 1) / pixelsPerByte;
166}
167
168/*
169 * Compute row bytes for an image using bytes per pixel
170 */
171static inline size_t compute_row_bytes_bpp(int width, uint32_t bytesPerPixel) {
172    return width * bytesPerPixel;
173}
174
175/*
176 * Compute row bytes for an image
177 */
178static inline size_t compute_row_bytes(int width, uint32_t bitsPerPixel) {
179    if (bitsPerPixel < 16) {
180        SkASSERT(0 == 8 % bitsPerPixel);
181        const uint32_t pixelsPerByte = 8 / bitsPerPixel;
182        return compute_row_bytes_ppb(width, pixelsPerByte);
183    } else {
184        SkASSERT(0 == bitsPerPixel % 8);
185        const uint32_t bytesPerPixel = bitsPerPixel / 8;
186        return compute_row_bytes_bpp(width, bytesPerPixel);
187    }
188}
189
190/*
191 * Get a byte from a buffer
192 * This method is unsafe, the caller is responsible for performing a check
193 */
194static inline uint8_t get_byte(uint8_t* buffer, uint32_t i) {
195    return buffer[i];
196}
197
198/*
199 * Get a short from a buffer
200 * This method is unsafe, the caller is responsible for performing a check
201 */
202static inline uint16_t get_short(uint8_t* buffer, uint32_t i) {
203    uint16_t result;
204    memcpy(&result, &(buffer[i]), 2);
205#ifdef SK_CPU_BENDIAN
206    return SkEndianSwap16(result);
207#else
208    return result;
209#endif
210}
211
212/*
213 * Get an int from a buffer
214 * This method is unsafe, the caller is responsible for performing a check
215 */
216static inline uint32_t get_int(uint8_t* buffer, uint32_t i) {
217    uint32_t result;
218    memcpy(&result, &(buffer[i]), 4);
219#ifdef SK_CPU_BENDIAN
220    return SkEndianSwap32(result);
221#else
222    return result;
223#endif
224}
225
226/*
227 * @param data           Buffer to read bytes from
228 * @param isLittleEndian Output parameter
229 *                       Indicates if the data is little endian
230 *                       Is unaffected on false returns
231 */
232static inline bool is_valid_endian_marker(const uint8_t* data, bool* isLittleEndian) {
233    // II indicates Intel (little endian) and MM indicates motorola (big endian).
234    if (('I' != data[0] || 'I' != data[1]) && ('M' != data[0] || 'M' != data[1])) {
235        return false;
236    }
237
238    *isLittleEndian = ('I' == data[0]);
239    return true;
240}
241
242static inline uint16_t get_endian_short(const uint8_t* data, bool littleEndian) {
243    if (littleEndian) {
244        return (data[1] << 8) | (data[0]);
245    }
246
247    return (data[0] << 8) | (data[1]);
248}
249
250static inline SkPMColor premultiply_argb_as_rgba(U8CPU a, U8CPU r, U8CPU g, U8CPU b) {
251    if (a != 255) {
252        r = SkMulDiv255Round(r, a);
253        g = SkMulDiv255Round(g, a);
254        b = SkMulDiv255Round(b, a);
255    }
256
257    return SkPackARGB_as_RGBA(a, r, g, b);
258}
259
260static inline SkPMColor premultiply_argb_as_bgra(U8CPU a, U8CPU r, U8CPU g, U8CPU b) {
261    if (a != 255) {
262        r = SkMulDiv255Round(r, a);
263        g = SkMulDiv255Round(g, a);
264        b = SkMulDiv255Round(b, a);
265    }
266
267    return SkPackARGB_as_BGRA(a, r, g, b);
268}
269
270static inline bool is_rgba(SkColorType colorType) {
271#ifdef SK_PMCOLOR_IS_RGBA
272    return (kBGRA_8888_SkColorType != colorType);
273#else
274    return (kRGBA_8888_SkColorType == colorType);
275#endif
276}
277
278// Method for coverting to a 32 bit pixel.
279typedef uint32_t (*PackColorProc)(U8CPU a, U8CPU r, U8CPU g, U8CPU b);
280
281static inline PackColorProc choose_pack_color_proc(bool isPremul, SkColorType colorType) {
282    bool isRGBA = is_rgba(colorType);
283    if (isPremul) {
284        if (isRGBA) {
285            return &premultiply_argb_as_rgba;
286        } else {
287            return &premultiply_argb_as_bgra;
288        }
289    } else {
290        if (isRGBA) {
291            return &SkPackARGB_as_RGBA;
292        } else {
293            return &SkPackARGB_as_BGRA;
294        }
295    }
296}
297
298static inline bool needs_premul(const SkImageInfo& dstInfo, const SkEncodedInfo& encodedInfo) {
299    return kPremul_SkAlphaType == dstInfo.alphaType() &&
300           SkEncodedInfo::kUnpremul_Alpha == encodedInfo.alpha();
301}
302
303static inline bool needs_color_xform(const SkImageInfo& dstInfo, const SkImageInfo& srcInfo,
304                                     bool needsColorCorrectPremul) {
305    // We never perform a color xform in legacy mode.
306    if (!dstInfo.colorSpace()) {
307        return false;
308    }
309
310    // F16 is by definition a linear space, so we always must perform a color xform.
311    bool isF16 = kRGBA_F16_SkColorType == dstInfo.colorType();
312
313    // Need a color xform when dst space does not match the src.
314    bool srcDstNotEqual =
315            !SkColorSpace_Base::EqualsIgnoreFlags(srcInfo.colorSpace(), dstInfo.colorSpace());
316
317    return needsColorCorrectPremul || isF16 || srcDstNotEqual;
318}
319
320static inline SkAlphaType select_xform_alpha(SkAlphaType dstAlphaType, SkAlphaType srcAlphaType) {
321    return (kOpaque_SkAlphaType == srcAlphaType) ? kOpaque_SkAlphaType : dstAlphaType;
322}
323
324static inline bool apply_xform_on_decode(SkColorType dstColorType, SkEncodedInfo::Color srcColor) {
325    // We will apply the color xform when reading the color table, unless F16 is requested.
326    return SkEncodedInfo::kPalette_Color != srcColor || kRGBA_F16_SkColorType == dstColorType;
327}
328
329/*
330 * Alpha Type Conversions
331 * - kOpaque to kOpaque, kUnpremul, kPremul is valid
332 * - kUnpremul to kUnpremul, kPremul is valid
333 *
334 * Color Type Conversions
335 * - Always support kRGBA_8888, kBGRA_8888
336 * - Support kRGBA_F16 when there is a linear dst color space
337 * - Support kIndex8 if it matches the src
338 * - Support k565 if kOpaque and color correction is not required
339 * - Support k565 if it matches the src, kOpaque, and color correction is not required
340 */
341static inline bool conversion_possible(const SkImageInfo& dst, const SkImageInfo& src) {
342    // Ensure the alpha type is valid.
343    if (!valid_alpha(dst.alphaType(), src.alphaType())) {
344        return false;
345    }
346
347    // Check for supported color types.
348    switch (dst.colorType()) {
349        case kRGBA_8888_SkColorType:
350        case kBGRA_8888_SkColorType:
351            return true;
352        case kRGBA_F16_SkColorType:
353            return dst.colorSpace() && dst.colorSpace()->gammaIsLinear();
354        case kIndex_8_SkColorType:
355            return kIndex_8_SkColorType == src.colorType();
356        case kRGB_565_SkColorType:
357            return kOpaque_SkAlphaType == src.alphaType() && !needs_color_xform(dst, src, false);
358        case kGray_8_SkColorType:
359            return kGray_8_SkColorType == src.colorType() &&
360                   kOpaque_SkAlphaType == src.alphaType() && !needs_color_xform(dst, src, false);
361        default:
362            return false;
363    }
364}
365
366#endif // SkCodecPriv_DEFINED
367