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1/*
2 * The MIT License (MIT)
3 *
4 * Copyright (c) 2014 Jan Solanti
5 *
6 * Permission is hereby granted, free of charge, to any person obtaining a copy
7 * of this software and associated documentation files (the "Software"), to deal
8 * in the Software without restriction, including without limitation the rights
9 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
10 * copies of the Software, and to permit persons to whom the Software is
11 * furnished to do so, subject to the following conditions:
12 *
13 * The above copyright notice and this permission notice shall be included in all
14 * copies or substantial portions of the Software.
15 *
16 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
17 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
18 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
19 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
20 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
21 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
22 * SOFTWARE.
23 */
24
25#include <stdio.h>
26#include <stdlib.h>
27#include <string.h>
28
29#ifndef LUPNG_USE_ZLIB
30#include <miniz.h>
31#else
32#include <zlib.h>
33#endif
34
35#include "lupng.h"
36
37#define PNG_NONE 0
38#define PNG_IHDR 0x01
39#define PNG_PLTE 0x02
40#define PNG_IDAT 0x04
41#define PNG_IEND 0x08
42
43#define PNG_GRAYSCALE 0
44#define PNG_TRUECOLOR 2
45/* 24bpp RGB palette */
46#define PNG_PALETTED 3
47#define PNG_GRAYSCALE_ALPHA 4
48#define PNG_TRUECOLOR_ALPHA 6
49
50#define PNG_FILTER_NONE 0
51#define PNG_FILTER_SUB 1
52#define PNG_FILTER_UP 2
53#define PNG_FILTER_AVERAGE 3
54#define PNG_FILTER_PAETH 4
55
56#define PNG_SIG_SIZE 8
57
58#define PNG_DONE 1
59#define PNG_OK 0
60#define PNG_ERROR -1
61
62#define BUF_SIZE 8192
63#define MAX(x, y) (x > y ? x : y)
64
65
66
67/********************************************************
68 * CRC computation as per PNG spec
69 ********************************************************/
70
71/* Precomputed table of CRCs of all 8-bit messages
72 using the polynomial from the PNG spec, 0xEDB88320L. */
73static const uint32_t crcTable[] =
74{
75    0x0, 0x77073096, 0xEE0E612C, 0x990951BA, 0x76DC419, 0x706AF48F,
76    0xE963A535, 0x9E6495A3, 0xEDB8832, 0x79DCB8A4, 0xE0D5E91E, 0x97D2D988,
77    0x9B64C2B, 0x7EB17CBD, 0xE7B82D07, 0x90BF1D91, 0x1DB71064, 0x6AB020F2,
78    0xF3B97148, 0x84BE41DE, 0x1ADAD47D, 0x6DDDE4EB, 0xF4D4B551, 0x83D385C7,
79    0x136C9856, 0x646BA8C0, 0xFD62F97A, 0x8A65C9EC, 0x14015C4F, 0x63066CD9,
80    0xFA0F3D63, 0x8D080DF5, 0x3B6E20C8, 0x4C69105E, 0xD56041E4, 0xA2677172,
81    0x3C03E4D1, 0x4B04D447, 0xD20D85FD, 0xA50AB56B, 0x35B5A8FA, 0x42B2986C,
82    0xDBBBC9D6, 0xACBCF940, 0x32D86CE3, 0x45DF5C75, 0xDCD60DCF, 0xABD13D59,
83    0x26D930AC, 0x51DE003A, 0xC8D75180, 0xBFD06116, 0x21B4F4B5, 0x56B3C423,
84    0xCFBA9599, 0xB8BDA50F, 0x2802B89E, 0x5F058808, 0xC60CD9B2, 0xB10BE924,
85    0x2F6F7C87, 0x58684C11, 0xC1611DAB, 0xB6662D3D, 0x76DC4190, 0x1DB7106,
86    0x98D220BC, 0xEFD5102A, 0x71B18589, 0x6B6B51F, 0x9FBFE4A5, 0xE8B8D433,
87    0x7807C9A2, 0xF00F934, 0x9609A88E, 0xE10E9818, 0x7F6A0DBB, 0x86D3D2D,
88    0x91646C97, 0xE6635C01, 0x6B6B51F4, 0x1C6C6162, 0x856530D8, 0xF262004E,
89    0x6C0695ED, 0x1B01A57B, 0x8208F4C1, 0xF50FC457, 0x65B0D9C6, 0x12B7E950,
90    0x8BBEB8EA, 0xFCB9887C, 0x62DD1DDF, 0x15DA2D49, 0x8CD37CF3, 0xFBD44C65,
91    0x4DB26158, 0x3AB551CE, 0xA3BC0074, 0xD4BB30E2, 0x4ADFA541, 0x3DD895D7,
92    0xA4D1C46D, 0xD3D6F4FB, 0x4369E96A, 0x346ED9FC, 0xAD678846, 0xDA60B8D0,
93    0x44042D73, 0x33031DE5, 0xAA0A4C5F, 0xDD0D7CC9, 0x5005713C, 0x270241AA,
94    0xBE0B1010, 0xC90C2086, 0x5768B525, 0x206F85B3, 0xB966D409, 0xCE61E49F,
95    0x5EDEF90E, 0x29D9C998, 0xB0D09822, 0xC7D7A8B4, 0x59B33D17, 0x2EB40D81,
96    0xB7BD5C3B, 0xC0BA6CAD, 0xEDB88320, 0x9ABFB3B6, 0x3B6E20C, 0x74B1D29A,
97    0xEAD54739, 0x9DD277AF, 0x4DB2615, 0x73DC1683, 0xE3630B12, 0x94643B84,
98    0xD6D6A3E, 0x7A6A5AA8, 0xE40ECF0B, 0x9309FF9D, 0xA00AE27, 0x7D079EB1,
99    0xF00F9344, 0x8708A3D2, 0x1E01F268, 0x6906C2FE, 0xF762575D, 0x806567CB,
100    0x196C3671, 0x6E6B06E7, 0xFED41B76, 0x89D32BE0, 0x10DA7A5A, 0x67DD4ACC,
101    0xF9B9DF6F, 0x8EBEEFF9, 0x17B7BE43, 0x60B08ED5, 0xD6D6A3E8, 0xA1D1937E,
102    0x38D8C2C4, 0x4FDFF252, 0xD1BB67F1, 0xA6BC5767, 0x3FB506DD, 0x48B2364B,
103    0xD80D2BDA, 0xAF0A1B4C, 0x36034AF6, 0x41047A60, 0xDF60EFC3, 0xA867DF55,
104    0x316E8EEF, 0x4669BE79, 0xCB61B38C, 0xBC66831A, 0x256FD2A0, 0x5268E236,
105    0xCC0C7795, 0xBB0B4703, 0x220216B9, 0x5505262F, 0xC5BA3BBE, 0xB2BD0B28,
106    0x2BB45A92, 0x5CB36A04, 0xC2D7FFA7, 0xB5D0CF31, 0x2CD99E8B, 0x5BDEAE1D,
107    0x9B64C2B0, 0xEC63F226, 0x756AA39C, 0x26D930A, 0x9C0906A9, 0xEB0E363F,
108    0x72076785, 0x5005713, 0x95BF4A82, 0xE2B87A14, 0x7BB12BAE, 0xCB61B38,
109    0x92D28E9B, 0xE5D5BE0D, 0x7CDCEFB7, 0xBDBDF21, 0x86D3D2D4, 0xF1D4E242,
110    0x68DDB3F8, 0x1FDA836E, 0x81BE16CD, 0xF6B9265B, 0x6FB077E1, 0x18B74777,
111    0x88085AE6, 0xFF0F6A70, 0x66063BCA, 0x11010B5C, 0x8F659EFF, 0xF862AE69,
112    0x616BFFD3, 0x166CCF45, 0xA00AE278, 0xD70DD2EE, 0x4E048354, 0x3903B3C2,
113    0xA7672661, 0xD06016F7, 0x4969474D, 0x3E6E77DB, 0xAED16A4A, 0xD9D65ADC,
114    0x40DF0B66, 0x37D83BF0, 0xA9BCAE53, 0xDEBB9EC5, 0x47B2CF7F, 0x30B5FFE9,
115    0xBDBDF21C, 0xCABAC28A, 0x53B39330, 0x24B4A3A6, 0xBAD03605, 0xCDD70693,
116    0x54DE5729, 0x23D967BF, 0xB3667A2E, 0xC4614AB8, 0x5D681B02, 0x2A6F2B94,
117    0xB40BBE37, 0xC30C8EA1, 0x5A05DF1B, 0x2D02EF8D
118};
119
120/* Update a running CRC with the bytes buf[0..len-1]--the CRC
121 should be initialized to all 1's, and the transmitted value
122 is the 1's complement of the final running CRC (see the
123 crc() routine below)). */
124static uint32_t updateCrc(uint32_t crc, unsigned char *buf,
125                          int len)
126{
127    unsigned long c = crc;
128    int n;
129
130    for (n = 0; n < len; n++)
131        c = crcTable[(c ^ buf[n]) & 0xFF] ^ (c >> 8);
132
133    return c;
134}
135
136/* Return the CRC of the bytes buf[0..len-1]. */
137static uint32_t crc(unsigned char *buf, int len)
138{
139    return updateCrc(0xFFFFFFFFL, buf, len) ^ 0xFFFFFFFFL;
140}
141
142
143
144/********************************************************
145 * Helper structs
146 ********************************************************/
147
148typedef struct
149{
150    uint32_t length;
151    uint8_t *type;
152    uint8_t *data;
153    uint32_t crc;
154} PngChunk;
155
156typedef struct {
157    void *userPtr;
158    PngReadProc readProc;
159    PngWriteProc writeProc;
160    int8_t chunksFound;
161
162    /* IHDR info */
163    uint32_t width;
164    uint32_t height;
165    uint8_t depth;
166    uint8_t colorType;
167    uint8_t channels;
168    uint8_t compression;
169    uint8_t filter;
170    uint8_t interlace;
171
172    /* PLTE info */
173    uint32_t paletteItems;
174    uint8_t *palette;
175
176    /* fields used for (de)compression & (de-)filtering */
177    z_stream stream;
178    size_t scanlineBytes;
179    int32_t currentCol;
180    int32_t currentRow;
181    uint32_t currentElem;
182    size_t currentByte;
183    int bytesPerPixel;
184    uint8_t *currentScanline;
185    uint8_t *previousScanline;
186    uint8_t currentFilter;
187    uint8_t interlacePass;
188    size_t compressedBytes;
189
190    /* used for constructing 16 bit deep pixels */
191    int tmpCount;
192    uint8_t tmpBytes[2];
193
194    /* the output image */
195    LuImage *img;
196} PngInfoStruct;
197
198/* PNG header: */
199static const uint8_t PNG_SIG[] =
200/*        P     N     G    \r    \n   SUB    \n   */
201{0x89, 0x50, 0x4E, 0x47, 0x0D, 0x0A, 0x1A, 0x0A};
202
203static const int startingRow[] =  { 0, 0, 0, 4, 0, 2, 0, 1 };
204static const int startingCol[] =  { 0, 0, 4, 0, 2, 0, 1, 0 };
205static const int rowIncrement[] = { 1, 8, 8, 8, 4, 4, 2, 2 };
206static const int colIncrement[] = { 1, 8, 8, 4, 4, 2, 2, 1 };
207
208
209
210/********************************************************
211 * Helper functions
212 ********************************************************/
213
214static inline void releaseChunk(PngChunk *chunk)
215{
216    /* Only release chunk->type since chunk->data points to the same memory. */
217    free((void *)chunk->type);
218    free((void *)chunk);
219}
220
221static inline uint32_t swap32(uint32_t n)
222{
223    union {
224        unsigned char np[4];
225        uint32_t i;
226    } u;
227    u.i = n;
228
229    return ((uint32_t)u.np[0] << 24)  |
230    ((uint32_t)u.np[1] << 16) |
231    ((uint32_t)u.np[2] << 8)  |
232    (uint32_t)u.np[3];
233}
234
235static inline uint16_t swap16(uint16_t n)
236{
237    union {
238        unsigned char np[2];
239        uint16_t i;
240    } u;
241    u.i = n;
242
243    return ((uint16_t)u.np[0] << 8) | (uint16_t)u.np[1];
244}
245
246static int bytesEqual(const uint8_t *a, const uint8_t *b, size_t count)
247{
248    size_t i;
249    for (i = 0; i < count; ++i)
250    {
251        if (*(a+i) != *(b+i))
252            return 0;
253    }
254
255    return 1;
256}
257
258
259
260/********************************************************
261 * Png filter functions
262 ********************************************************/
263static inline int absi(int val)
264{
265    return val > 0 ? val : -val;
266}
267
268static inline uint8_t raw(PngInfoStruct *info, int32_t col)
269{
270    if (col < 0)
271        return 0;
272    return info->currentScanline[col];
273}
274
275static inline uint8_t prior(PngInfoStruct *info, int32_t col)
276{
277    if (info->currentRow <= startingRow[info->interlacePass] || col < 0)
278        return 0;
279    return info->previousScanline[col];
280}
281
282static inline uint8_t paethPredictor(uint8_t a, uint8_t b, uint8_t c)
283{
284    unsigned int A = a, B = b, C = c;
285    int p = (int)A + (int)B - (int)C;
286    int pa = absi(p - (int)A);
287    int pb = absi(p - (int)B);
288    int pc = absi(p - (int)C);
289
290    if (pa <= pb && pa <= pc)
291        return a;
292    if (pb <= pc)
293        return b;
294    return c;
295}
296
297static inline uint8_t deSub(PngInfoStruct *info, uint8_t filtered)
298{
299    return filtered + raw(info, info->currentByte-info->bytesPerPixel);
300}
301
302static inline uint8_t deUp(PngInfoStruct *info, uint8_t filtered)
303{
304    return filtered + prior(info, info->currentByte);
305}
306
307static inline uint8_t deAverage(PngInfoStruct *info, uint8_t filtered)
308{
309    uint16_t avg = (uint16_t)(raw(info, info->currentByte-info->bytesPerPixel)
310                                + prior(info, info->currentByte));
311    avg >>= 1;
312    return filtered + avg;
313}
314
315static inline uint8_t dePaeth(PngInfoStruct *info, uint8_t filtered)
316{
317    return filtered + paethPredictor(
318                        raw(info, info->currentByte-info->bytesPerPixel),
319                        prior(info, info->currentByte),
320                        prior(info, info->currentByte-info->bytesPerPixel));
321}
322
323static inline uint8_t none(PngInfoStruct *info)
324{
325    return raw(info, info->currentByte);
326}
327
328static inline uint8_t sub(PngInfoStruct *info)
329{
330    return raw(info, info->currentByte) - raw(info, info->currentByte-info->bytesPerPixel);
331}
332
333static inline uint8_t up(PngInfoStruct *info)
334{
335    return raw(info, info->currentByte) - prior(info, info->currentByte);
336}
337
338static inline uint8_t average(PngInfoStruct *info)
339{
340    uint16_t avg = (uint16_t)(raw(info, info->currentByte-info->bytesPerPixel)
341                              + prior(info, info->currentByte));
342    avg >>= 1;
343    return raw(info, info->currentByte) - avg;
344}
345
346static inline uint8_t paeth(PngInfoStruct *info)
347{
348    return raw(info, info->currentByte) - paethPredictor(
349                    raw(info, info->currentByte-info->bytesPerPixel),
350                    prior(info, info->currentByte),
351                    prior(info, info->currentByte-info->bytesPerPixel));
352}
353
354
355
356/********************************************************
357 * Actual implementation
358 ********************************************************/
359static inline int parseIhdr(PngInfoStruct *info, PngChunk *chunk)
360{
361    if (info->chunksFound)
362    {
363        printf("PNG: malformed PNG file!\n");
364        return PNG_ERROR;
365    }
366
367    info->chunksFound |= PNG_IHDR;
368    info->width = swap32(*(uint32_t *)chunk->data);
369    info->height = swap32(*((uint32_t *)chunk->data + 1));
370    info->depth = *(chunk->data + 8);
371    info->colorType = *(chunk->data + 9);
372    info->compression = *(chunk->data + 10);
373    info->filter = *(chunk->data + 11);
374    info->interlace = *(chunk->data + 12);
375
376    switch (info->colorType)
377    {
378        case PNG_GRAYSCALE:
379            info->channels = 1;
380            break;
381        case PNG_TRUECOLOR:
382            info->channels = 3;
383            break;
384        case PNG_PALETTED:
385            info->channels = 3;
386            break;
387        case PNG_GRAYSCALE_ALPHA:
388            info->channels = 2;
389            break;
390        case PNG_TRUECOLOR_ALPHA:
391            info->channels = 4;
392            break;
393        default:
394            printf("PNG: illegal color type: %i\n",
395                   (unsigned int)info->colorType);
396            return PNG_ERROR;
397            break;
398    }
399
400    if ((info->colorType != PNG_GRAYSCALE && info->colorType != PNG_PALETTED &&
401         info->depth < 8) ||
402        (info->colorType == PNG_PALETTED && info->depth == 16) ||
403        info->depth > 16)
404    {
405        printf("PNG: illegal bit depth for color type\n");
406        return PNG_ERROR;
407    }
408
409    if (info->compression)
410    {
411        printf("PNG: unknown compression method: %i\n",
412               (unsigned int)info->compression);
413        return PNG_ERROR;
414    }
415
416    if (info->filter)
417    {
418        printf("PNG: unknown filter scheme: %i\n",
419               (unsigned int)info->filter);
420        return PNG_ERROR;
421    }
422
423    memset(&(info->stream), 0, sizeof(info->stream));
424    if(inflateInit(&(info->stream)) != Z_OK)
425    {
426        printf("PNG: inflateInit failed!\n");
427        return PNG_ERROR;
428    }
429    info->img = luImageCreate(info->width, info->height,
430                              info->channels, info->depth < 16 ? 8 : 16);
431    info->scanlineBytes = MAX((info->width * info->channels * info->depth) >> 3, 1);
432    info->currentScanline = (uint8_t *)malloc(info->scanlineBytes);
433    info->previousScanline = (uint8_t *)malloc(info->scanlineBytes);
434    info->currentCol = -1;
435    info->interlacePass = info->interlace ? 1 : 0;
436    info->bytesPerPixel = MAX((info->channels * info->depth) >> 3, 1);
437    if (!info->img || !info->currentScanline || !info->previousScanline)
438    {
439        printf("PNG: memory allocation failed!\n");
440        return PNG_ERROR;
441    }
442
443    return PNG_OK;
444}
445
446static inline int parsePlte(PngInfoStruct *info, PngChunk *chunk)
447{
448    if (info->chunksFound & PNG_IDAT || !(info->chunksFound & PNG_IHDR))
449    {
450        printf("PNG: malformed PNG file!\n");
451        return PNG_ERROR;
452    }
453
454    info->chunksFound |= PNG_PLTE;
455
456    if (chunk->length % 3 != 0)
457    {
458        printf("PNG: invalid palette size!\n");
459        return PNG_ERROR;
460    }
461
462    info->paletteItems = chunk->length/3;
463    info->palette = (uint8_t *)malloc(chunk->length);
464    if (!info->palette)
465    {
466        printf("PNG: memory allocation failed!\n");
467        return PNG_ERROR;
468    }
469    memcpy(info->palette, chunk->data, chunk->length);
470
471    return PNG_OK;
472}
473
474static inline void stretchBits(uint8_t inByte, uint8_t outBytes[8], int depth)
475{
476    int i;
477    switch (depth) {
478        case 1:
479            for (i = 0; i < 8; ++i)
480                outBytes[i] = (inByte >> (7-i)) & 0x01;
481            break;
482
483        case 2:
484            outBytes[0] = (inByte >> 6) & 0x03;
485            outBytes[1] = (inByte >> 4) & 0x03;
486            outBytes[2] = (inByte >> 2) & 0x03;
487            outBytes[3] = inByte & 0x03;
488            break;
489
490        case 4:
491            outBytes[0] = (inByte >> 4) & 0x0F;
492            outBytes[1] = inByte & 0x0F;
493            break;
494
495        default:
496            break;
497    }
498}
499
500/* returns: 1 if at end of scanline, 0 otherwise */
501static inline int insertByte(PngInfoStruct *info, uint8_t byte)
502{
503    int advance = 0;
504    const uint8_t scale[] = {0x00, 0xFF, 0x55, 0x00, 0x11, 0x00, 0x00, 0x00};
505
506    /* for paletted images currentElem will always be 0 */
507    size_t idx = info->currentRow * info->width * info->channels
508                    + info->currentCol * info->channels
509                    + info->currentElem;
510
511    if (info->colorType != PNG_PALETTED)
512    {
513        if (info->depth == 8)
514            info->img->data[idx] = byte;
515
516        else if (info->depth < 8)
517            info->img->data[idx] = byte * scale[info->depth];
518
519        else /* depth == 16 */
520        {
521            info->tmpBytes[info->tmpCount] = byte;
522            if (info->tmpCount) /* just inserted 2nd byte */
523            {
524                uint16_t val = *(uint16_t *)info->tmpBytes;
525                val = swap16(val);
526                info->tmpCount = 0;
527
528                ((uint16_t *)(info->img->data))[idx] = val;
529            }
530            else
531            {
532                ++info->tmpCount;
533                return 0;
534            }
535        }
536
537        ++info->currentElem;
538        if (info->currentElem >= info->channels)
539        {
540            advance = 1;
541            info->currentElem = 0;
542        }
543    }
544    else
545    {
546        /* The spec limits palette size to 256 entries */
547        if (byte < info->paletteItems)
548        {
549            info->img->data[idx  ] = info->palette[3*byte  ];
550            info->img->data[idx+1] = info->palette[3*byte+1];
551            info->img->data[idx+2] = info->palette[3*byte+2];
552        }
553        else
554        {
555            printf("PNG: invalid palette index encountered!\n");
556        }
557        advance = 1;
558    }
559
560    if (advance)
561    {
562        /* advance to next pixel */
563        info->currentCol += colIncrement[info->interlacePass];
564
565        if (info->currentCol >= info->width)
566        {
567            uint8_t *tmp = info->currentScanline;
568            info->currentScanline = info->previousScanline;
569            info->previousScanline = tmp;
570
571            info->currentCol = -1;
572            info->currentByte = 0;
573
574            info->currentRow += rowIncrement[info->interlacePass];
575            if (info->currentRow >= info->height && info->interlace)
576            {
577                ++info->interlacePass;
578                while (startingCol[info->interlacePass] >= info->width ||
579                       startingRow[info->interlacePass] >= info->height)
580                    ++info->interlacePass;
581                info->currentRow = startingRow[info->interlacePass];
582            }
583            return 1;
584        }
585    }
586
587    return 0;
588}
589
590static inline int parseIdat(PngInfoStruct *info, PngChunk *chunk)
591{
592    unsigned char filtered[BUF_SIZE];
593    int status = Z_OK;
594
595    if (!(info->chunksFound & PNG_IHDR))
596    {
597        printf("PNG: malformed PNG file!\n");
598        return PNG_ERROR;
599    }
600
601    if (info->colorType == PNG_PALETTED && !(info->chunksFound & PNG_PLTE))
602    {
603        printf("PNG: palette required but missing!\n");
604        return PNG_ERROR;
605    }
606
607    info->chunksFound |= PNG_IDAT;
608    info->stream.next_in = (unsigned char *)chunk->data;
609    info->stream.avail_in = chunk->length;
610    do
611    {
612        info->stream.next_out = filtered;
613        info->stream.avail_out = BUF_SIZE;
614        status = inflate(&(info->stream), Z_NO_FLUSH);
615        size_t decompressed = BUF_SIZE - info->stream.avail_out;
616        size_t i;
617
618        if (status != Z_OK &&
619            status != Z_STREAM_END &&
620            status != Z_BUF_ERROR &&
621            status != Z_NEED_DICT)
622        {
623            printf("PNG: inflate error!\n");
624            return PNG_ERROR;
625        }
626
627        for (i = 0; i < decompressed; ++i)
628        {
629            if (info->currentCol < 0)
630            {
631                info->currentCol = startingCol[info->interlacePass];
632                info->currentFilter = filtered[i];
633            }
634            else
635            {
636                uint8_t rawByte = 0;
637                uint8_t fullBytes[8] = {0};
638                switch (info->currentFilter)
639                {
640                    case PNG_FILTER_NONE:
641                        rawByte = filtered[i];
642                        break;
643                    case PNG_FILTER_SUB:
644                        rawByte = deSub(info, filtered[i]);
645                        break;
646                    case PNG_FILTER_UP:
647                        rawByte = deUp(info, filtered[i]);
648                        break;
649                    case PNG_FILTER_AVERAGE:
650                        rawByte = deAverage(info, filtered[i]);
651                        break;
652                    case PNG_FILTER_PAETH:
653                        rawByte = dePaeth(info, filtered[i]);
654                        break;
655                    default:
656                        break;
657                }
658
659                info->currentScanline[info->currentByte] = rawByte;
660                ++info->currentByte;
661
662                if (info->depth < 8)
663                {
664                    int j;
665                    stretchBits(rawByte, fullBytes, info->depth);
666                    for (j = 0; j < 8/info->depth; ++j)
667                        if(insertByte(info, fullBytes[j]))
668                            break;
669                }
670                else
671                    insertByte(info, rawByte);
672            }
673        }
674    } while ((info->stream.avail_in > 0 || info->stream.avail_out == 0));
675
676    return PNG_OK;
677}
678
679static inline PngChunk *readChunk(PngInfoStruct *info)
680{
681    PngChunk *chunk = (PngChunk *)malloc(sizeof(PngChunk));
682    size_t read = 0;
683    if (!chunk)
684    {
685        printf("PNG: memory allocation failed!\n");
686        return 0;
687    }
688
689    info->readProc((void *)&chunk->length, 4, 1, info->userPtr);
690    chunk->length = swap32(chunk->length);
691    chunk->type = (uint8_t *)malloc(chunk->length + 4);
692    chunk->data = chunk->type + 4;
693
694    info->readProc((void *)chunk->type, 1, chunk->length + 4, info->userPtr);
695    read = info->readProc((void *)&chunk->crc, 4, 1, info->userPtr);
696    chunk->crc = swap32(chunk->crc);
697
698    if (read != 1)
699    {
700        printf("PNG: read error\n");
701        releaseChunk(chunk);
702        return 0;
703    }
704
705    if (crc(chunk->type, chunk->length+4) != chunk->crc)
706    {
707        printf("PNG: CRC mismatch in \'%.4s\'\n", (char *)chunk->type);
708        releaseChunk(chunk);
709        return 0;
710    }
711
712    return chunk;
713}
714
715static inline int handleChunk(PngInfoStruct *info, PngChunk *chunk)
716{
717    /* critical chunk */
718    if (!(chunk->type[0] & 0x20))
719    {
720        if (bytesEqual(chunk->type, (const uint8_t *)"IHDR", 4))
721            return parseIhdr(info, chunk);
722        if (bytesEqual(chunk->type, (const uint8_t *)"PLTE", 4))
723            return parsePlte(info, chunk);
724        if (bytesEqual(chunk->type, (const uint8_t *)"IDAT", 4))
725            return parseIdat(info, chunk);
726        if (bytesEqual(chunk->type, (const uint8_t *)"IEND", 4))
727        {
728            info->chunksFound |= PNG_IEND;
729            if (!(info->chunksFound & PNG_IDAT))
730            {
731                printf("PNG: no IDAT chunk found\n");
732                return PNG_ERROR;
733            }
734            return PNG_DONE;
735        }
736    }
737    /* ignore ancillary chunks for now */
738
739    return PNG_OK;
740}
741
742LuImage *luPngRead(PngReadProc readProc, void *userPtr)
743{
744    PngInfoStruct info =
745    {
746        userPtr,
747        readProc,
748        0,
749        PNG_NONE
750    };
751    uint8_t signature[PNG_SIG_SIZE];
752    int status = PNG_ERROR;
753
754    info.readProc((void *)signature, 1, PNG_SIG_SIZE, userPtr);
755    if (bytesEqual(signature, PNG_SIG, PNG_SIG_SIZE))
756    {
757        PngChunk *chunk;
758        while ((chunk = readChunk(&info)))
759        {
760            status = handleChunk(&info, chunk);
761            releaseChunk(chunk);
762
763            if (status != PNG_OK)
764                break;
765        }
766    }
767    else
768        printf("PNG: invalid header\n");
769
770    if (info.currentScanline)
771        free((void *)info.currentScanline);
772    if (info.previousScanline)
773        free((void *)info.previousScanline);
774    if (info.palette)
775        free((void *)info.palette);
776    inflateEnd(&info.stream);
777
778    if (status == PNG_DONE)
779        return info.img;
780    else
781        if (info.img)
782            luImageRelease(info.img);
783
784    return 0;
785}
786
787static inline int writeIhdr(PngInfoStruct *info)
788{
789    static uint8_t buf[17];
790    static const uint8_t colorType[] = {
791            PNG_GRAYSCALE,
792            PNG_GRAYSCALE_ALPHA,
793            PNG_TRUECOLOR,
794            PNG_TRUECOLOR_ALPHA
795    };
796    size_t written = 0;
797    PngChunk c;
798
799    if (info->img->channels > 4)
800    {
801        printf("PNG: too many channels in image\n");
802        return PNG_ERROR;
803    }
804
805    c.length = swap32(13);
806    c.type = buf; // 4 (type) + 4 + 4 + 5x1
807    c.data = c.type + 4;
808
809    memcpy((void *)c.type, (void *)"IHDR", 4);
810    *(uint32_t *)(c.data)     = swap32((uint32_t)info->img->width);
811    *(uint32_t *)(c.data + 4) = swap32((uint32_t)info->img->height);
812    *(c.data + 8)  = info->img->depth;
813    *(c.data + 9)  = colorType[info->img->channels-1];
814    *(c.data + 10) = 0; // compression method
815    *(c.data + 11) = 0; // filter method
816    *(c.data + 12) = 0; // interlace method: none
817
818    c.crc = swap32(crc(c.type, 17));
819
820    written += info->writeProc((void *)&c.length, 4, 1, info->userPtr) * 4;
821    written += info->writeProc((void *)c.type, 1, 4, info->userPtr);
822    written += info->writeProc((void *)c.data, 1, 13, info->userPtr);
823    written += info->writeProc((void *)&c.crc, 4, 1, info->userPtr) * 4;
824
825    if (written != 25)
826    {
827        printf("PNG: write error\n");
828        return PNG_ERROR;
829    }
830
831    return PNG_OK;
832}
833
834static inline int writeIdat(PngInfoStruct *info, uint8_t *buf, size_t buflen)
835{
836    size_t written = 0;
837    PngChunk c;
838
839    c.length = swap32(buflen-4);
840    c.crc = swap32(crc(buf, buflen));
841
842    written += info->writeProc((void *)&c.length, 4, 1, info->userPtr) * 4;
843    written += info->writeProc((void *)buf, 1, buflen, info->userPtr);
844    written += info->writeProc((void *)&c.crc, 4, 1, info->userPtr) * 4;
845
846    if (written != buflen+8)
847    {
848        printf("PNG: write error\n");
849        return PNG_ERROR;
850    }
851    
852    return PNG_OK;
853}
854
855static inline void advanceBytep(PngInfoStruct *info, int is16bit)
856{
857    if (is16bit)
858    {
859        if (info->currentByte%2)
860            --info->currentByte;
861        else
862            info->currentByte+=3;
863    }
864    else
865        ++info->currentByte;
866}
867
868static inline size_t filterScanline(PngInfoStruct *info,
869                                    uint8_t(*f)(PngInfoStruct *info),
870                                    uint8_t filter,
871                                    uint8_t *filterCandidate,
872                                    int is16bit)
873{
874    size_t curSum = 0;
875    filterCandidate[0] = filter;
876    size_t fc;
877    for (info->currentByte = is16bit ? 1 : 0, fc = 1;
878        info->currentByte < info->scanlineBytes; ++fc, advanceBytep(info, is16bit) )
879    {
880        uint8_t val = f(info);
881        filterCandidate[fc] = val;
882        curSum += val;
883    }
884
885    return curSum;
886}
887
888/*
889 * Processes the input image and calls writeIdat for every BUF_SIZE compressed
890 * bytes.
891 */
892static inline int processPixels(PngInfoStruct *info)
893{
894    uint8_t idatBuf[BUF_SIZE+4] = {'I', 'D', 'A', 'T'};
895    uint8_t *compressed = idatBuf+4;
896    uint8_t *filterCandidate = (uint8_t *)malloc(info->scanlineBytes+1);
897    uint8_t *bestCandidate = (uint8_t *)malloc(info->scanlineBytes+1);
898    size_t minSum = (size_t)-1, curSum = 0;
899    int status = Z_OK;
900    int is16bit = info->img->depth == 16;
901
902    if (!filterCandidate || !bestCandidate)
903    {
904        printf("PNG: memory allocation failed!\n");
905    }
906
907    memset(&(info->stream), 0, sizeof(info->stream));
908    if(deflateInit(&(info->stream), Z_DEFAULT_COMPRESSION) != Z_OK)
909    {
910        printf("PNG: deflateInit failed!\n");
911        free(filterCandidate);
912        free(bestCandidate);
913        return PNG_ERROR;
914    }
915
916    info->stream.avail_out = BUF_SIZE;
917    info->stream.next_out = compressed;
918
919    for (info->currentRow = 0; info->currentRow < info->img->height;
920         ++info->currentRow)
921    {
922        int flush = (info->currentRow < info->img->height-1) ?
923        Z_NO_FLUSH : Z_FINISH;
924        minSum = (size_t)-1;
925
926        /*
927         * 1st time it doesn't matter, the filters never look at the previous
928         * scanline when processing row 0. And next time it'll be valid.
929         */
930        info->previousScanline = info->currentScanline;
931        info->currentScanline = info->img->data + (info->currentRow*info->scanlineBytes);
932
933        /*
934         * Try to choose the best filter for each scanline.
935         * Breaks in case of overflow, but hey it's just a heuristic.
936         */
937        for (info->currentFilter = PNG_FILTER_NONE; info->currentFilter <= PNG_FILTER_PAETH; ++info->currentFilter)
938        {
939
940            switch (info->currentFilter)
941            {
942                case PNG_FILTER_NONE:
943                    curSum = filterScanline(info, none, PNG_FILTER_NONE, filterCandidate, is16bit);
944                    break;
945
946                case PNG_FILTER_SUB:
947                    curSum = filterScanline(info, sub, PNG_FILTER_SUB, filterCandidate, is16bit);
948                    break;
949
950                case PNG_FILTER_UP:
951                    curSum = filterScanline(info, up, PNG_FILTER_UP, filterCandidate, is16bit);
952                    break;
953
954                case PNG_FILTER_AVERAGE:
955                    curSum = filterScanline(info, average, PNG_FILTER_AVERAGE, filterCandidate, is16bit);
956                    break;
957
958                case PNG_FILTER_PAETH:
959                    curSum = filterScanline(info, paeth, PNG_FILTER_PAETH, filterCandidate, is16bit);
960                    break;
961
962                default:
963                    break;
964            }
965
966            if (curSum < minSum || !info->currentFilter)
967            {
968                uint8_t *tmp = bestCandidate;
969                bestCandidate = filterCandidate;
970                filterCandidate = tmp;
971                minSum = curSum;
972            }
973        }
974
975        info->stream.avail_in = info->scanlineBytes+1;
976        info->stream.next_in = bestCandidate;
977
978        // compress bestCandidate
979        do
980        {
981            status = deflate(&info->stream, flush);
982
983            if (info->stream.avail_out < BUF_SIZE)
984            {
985                writeIdat(info, idatBuf, BUF_SIZE-info->stream.avail_out+4);
986                info->stream.next_out = compressed;
987                info->stream.avail_out = BUF_SIZE;
988            }
989        } while ((flush == Z_FINISH && status != Z_STREAM_END)
990                    || (flush == Z_NO_FLUSH && info->stream.avail_in));
991        // TODO: fix loop conditions, apparently data gets truncated
992    }
993
994    return PNG_OK;
995}
996
997static inline int writeIend(PngInfoStruct *info)
998{
999    PngChunk c = { 0, (uint8_t *)"IEND", 0, 0 };
1000    size_t written = 0;
1001    c.crc = swap32(crc(c.type, 4));
1002
1003    written += info->writeProc((void *)&c.length, 4, 1, info->userPtr) * 4;
1004    written += info->writeProc((void *)c.type, 1, 4, info->userPtr);
1005    written += info->writeProc((void *)&c.crc, 4, 1, info->userPtr) * 4;
1006
1007    if (written != 12)
1008    {
1009        printf("PNG: write error\n");
1010        return PNG_ERROR;
1011    }
1012
1013    return PNG_OK;
1014}
1015
1016int luPngWrite(PngWriteProc writeProc, void *userPtr, LuImage *img)
1017{
1018    PngInfoStruct info = {
1019        userPtr,
1020        0,
1021        writeProc,
1022        PNG_NONE
1023    };
1024
1025    info.img = img;
1026    info.bytesPerPixel = (info.img->channels * info.img->depth) >> 3;
1027
1028    if (writeProc((void *)PNG_SIG, 1, PNG_SIG_SIZE, userPtr) != PNG_SIG_SIZE)
1029    {
1030        printf("PNG: write error\n");
1031        return PNG_ERROR;
1032    }
1033
1034    if (writeIhdr(&info) != PNG_OK)
1035        return PNG_ERROR;
1036
1037    info.scanlineBytes = (img->depth >> 3) * img->channels * img->width;
1038    if (processPixels(&info) != PNG_OK)
1039    {
1040        deflateEnd(&(info.stream));
1041        return PNG_ERROR;
1042    }
1043
1044    deflateEnd(&(info.stream));
1045    return writeIend(&info);
1046}
1047
1048
1049void luImageRelease(LuImage *img)
1050{
1051    free((void *)img->data);
1052    free((void *)img);
1053}
1054
1055LuImage *luImageCreate(size_t width, size_t height, uint8_t channels, uint8_t depth)
1056{
1057    LuImage *img;
1058
1059    if (depth != 8 && depth != 16)
1060    {
1061        printf("Image: only bit depths 8 and 16 are supported!\n");
1062        return 0;
1063    }
1064
1065    img = (LuImage *)malloc(sizeof(LuImage));
1066    if (!img)
1067        return 0;
1068
1069    img->width = width;
1070    img->height = height;
1071    img->channels = channels;
1072    img->depth = depth;
1073    img->dataSize = (size_t)((depth >> 3) * width * height * channels);
1074    img->data = (uint8_t *)malloc(img->dataSize);
1075
1076    return img;
1077}
1078

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