2  * pnglite.c - pnglite library
24 #define	abs(x)	((x) < 0? -(x):(x))
44 		result = lseek(png->fd, offset, SEEK_CUR);  in file_read()
46 		result = read(png->fd, out, size * numel);  in file_read()
76 	switch (png->color_type) {  in png_get_bpp()
91 	bpp *= png->depth / 8;  in png_get_bpp()
123 	png->width = get_ul(ihdr+4);  in png_read_ihdr()
124 	png->height = get_ul(ihdr+8);  in png_read_ihdr()
125 	png->depth = ihdr[12];  in png_read_ihdr()
126 	png->color_type = ihdr[13];  in png_read_ihdr()
127 	png->compression_method = ihdr[14];  in png_read_ihdr()
128 	png->filter_method = ihdr[15];  in png_read_ihdr()
129 	png->interlace_method = ihdr[16];  in png_read_ihdr()
131 	if (png->color_type == PNG_INDEXED)  in png_read_ihdr()
134 	if (png->depth != 8 && png->depth != 16)  in png_read_ihdr()
137 	if (png->interlace_method)  in png_read_ihdr()
147 	printf("\twidth:\t\t%d\n", png->width);  in png_print_info()
148 	printf("\theight:\t\t%d\n", png->height);  in png_print_info()
149 	printf("\tdepth:\t\t%d\n", png->depth);  in png_print_info()
152 	switch (png->color_type) {  in png_print_info()
168 	    png->compression_method?  in png_print_info()
171 	    png->filter_method? "unknown, this is not good":"adaptive");  in png_print_info()
173 	    png->interlace_method? "interlace":"no interlace");  in png_print_info()
182 	png->image = NULL;  in png_open()
183 	png->fd = open(filename, O_RDONLY);  in png_open()
184 	if (png->fd == -1)  in png_open()
201 			png->bpp = (uint8_t)result;  in png_open()
208 		uint64_t size = png->width * png->height * png->bpp;  in png_open()
211 			png->image = malloc(size);  in png_open()
212 		if (png->image == NULL)  in png_open()
217 		result = png_get_data(png, png->image);  in png_open()
220 		free(png->image);  in png_open()
221 		(void) close(png->fd);  in png_open()
222 		png->fd = -1;  in png_open()
232 	(void) close(png->fd);  in png_close()
233 	png->fd = -1;  in png_close()
234 	free(png->image);  in png_close()
235 	png->image = NULL;  in png_close()
244 	png->zs = calloc(1, sizeof (z_stream));  in png_init_inflate()
246 	stream = png->zs;  in png_init_inflate()
252 		free(png->zs);  in png_init_inflate()
253 		png->zs = NULL;  in png_init_inflate()
257 	stream->next_out = png->png_data;  in png_init_inflate()
258 	stream->avail_out = png->png_datalen;  in png_init_inflate()
266 	z_stream *stream = png->zs;  in png_end_inflate()
273 		printf("ZLIB says: %s\n", stream->msg);  in png_end_inflate()
277 	free(png->zs);  in png_end_inflate()
278 	png->zs = NULL;  in png_end_inflate()
284 png_inflate(png_t *png, uint8_t *data, int len)  in png_inflate()  argument
287 	z_stream *stream = png->zs;  in png_inflate()
292 	stream->next_in = data;  in png_inflate()
293 	stream->avail_in = len;  in png_inflate()
298 		printf("%s\n", stream->msg);  in png_inflate()
302 	if (stream->avail_in != 0)  in png_inflate()
315 	if (!png->readbuf || png->readbuflen < length) {  in png_read_idat()
316 		png->readbuf = realloc(png->readbuf, length);  in png_read_idat()
317 		png->readbuflen = length;  in png_read_idat()
320 	if (!png->readbuf)  in png_read_idat()
323 	if (file_read(png, png->readbuf, 1, length) != len)  in png_read_idat()
328 	calc_crc = crc32(calc_crc, (uint8_t *)png->readbuf, length);  in png_read_idat()
336 	return (png_inflate(png, png->readbuf, length));  in png_read_idat()
357 		if (!png->png_data) {	/* first IDAT */  in png_process_chunk()
358 			png->png_datalen = png->width * png->height *  in png_process_chunk()
359 			    png->bpp + png->height;  in png_process_chunk()
360 			png->png_data = malloc(png->png_datalen);  in png_process_chunk()
363 		if (!png->png_data)  in png_process_chunk()
366 		if (!png->zs) {  in png_process_chunk()
389 			a = out[i - stride];  in png_filter_sub()
422 			a = out[i - stride];  in png_filter_average()
434 	int p = (int)a + b - c;  in png_paeth()
435 	int pa = abs(p - a);  in png_paeth()
436 	int pb = abs(p - b);  in png_paeth()
437 	int pc = abs(p - c);  in png_paeth()
462 			a = out[i - stride];  in png_filter_paeth()
464 			c = prev_line[i - stride];  in png_filter_paeth()
472 				a = out[i - stride];  in png_filter_paeth()
484 png_unfilter(png_t *png, uint8_t *data)  in png_unfilter()  argument
489 	uint8_t *filtered = png->png_data;  in png_unfilter()
490 	unsigned stride = png->bpp;  in png_unfilter()
492 	while (pos < png->png_datalen) {  in png_unfilter()
497 		if (png->depth == 16) {  in png_unfilter()
498 			for (i = 0; i < png->width * stride; i += 2) {  in png_unfilter()
506 			memcpy(data+outpos, filtered+pos, png->width * stride);  in png_unfilter()
509 			png_filter_sub(stride, filtered+pos, data+outpos,  in png_unfilter()
510 			    png->width * stride);  in png_unfilter()
514 				png_filter_up(stride, filtered+pos, data+outpos,  in png_unfilter()
515 				    data + outpos - (png->width*stride),  in png_unfilter()
516 				    png->width*stride);  in png_unfilter()
518 				png_filter_up(stride, filtered+pos, data+outpos,  in png_unfilter()
519 				    0, png->width*stride);  in png_unfilter()
525 				    data+outpos,  in png_unfilter()
526 				    data + outpos - (png->width*stride),  in png_unfilter()
527 				    png->width*stride);  in png_unfilter()
530 				    data+outpos, 0, png->width*stride);  in png_unfilter()
536 				    data+outpos,  in png_unfilter()
537 				    data + outpos - (png->width*stride),  in png_unfilter()
538 				    png->width*stride);  in png_unfilter()
541 				    data+outpos, 0, png->width*stride);  in png_unfilter()
548 		outpos += png->width * stride;  in png_unfilter()
549 		pos += png->width * stride;  in png_unfilter()
556 png_get_data(png_t *png, uint8_t *data)  in png_get_data()  argument
560 	png->zs = NULL;  in png_get_data()
561 	png->png_datalen = 0;  in png_get_data()
562 	png->png_data = NULL;  in png_get_data()
563 	png->readbuf = NULL;  in png_get_data()
564 	png->readbuflen = 0;  in png_get_data()
569 	if (png->readbuf) {  in png_get_data()
570 		free(png->readbuf);  in png_get_data()
571 		png->readbuflen = 0;  in png_get_data()
573 	if (png->zs)  in png_get_data()
577 		free(png->png_data);  in png_get_data()
581 	result = png_unfilter(png, data);  in png_get_data()
583 	free(png->png_data);  in png_get_data()