this is starting to hurt my head

include/cammy/image.h

@@ -11,6 +11,9 @@
 
 #define CAMMY_IMAGE_CHUNK_SIZE 4096
 
+#define CAMMY_IMAGE_MAGIC_TILE "TILE"
+#define CAMMY_IMAGE_MAGIC_PNG  "\x89PNG"
+
 typedef enum {
     CAMMY_IMAGE_NONE,
     CAMMY_IMAGE_2BPP_TILE,
@@ -29,8 +32,18 @@ typedef struct _cammy_image {
            uint8_t *buf;
         cammy_tile *tiles;
     };
+
+    char *file;
 } cammy_image;
 
+#define CAMMY_IMAGE_HEADER_VERSION 0x0001
+
+typedef struct _cammy_image_header {
+    uint8_t magic[4];
+    uint16_t version;
+    uint16_t width, height;
+} cammy_image_header;
+
 typedef struct _cammy_image_point {
     size_t x, y;
 } cammy_image_point;
@@ -43,25 +56,12 @@ cammy_image *cammy_image_new(cammy_image_format format,
                              size_t width,
                              size_t height);
 
-void cammy_image_close(cammy_image *image);
+cammy_image *cammy_image_open(const char *filename);
 
 void cammy_image_destroy(cammy_image *image);
 
-cammy_image *cammy_image_open_tile(const char *filename,
-                                   size_t width,
-                                   size_t height);
-
-int cammy_image_save_tile(cammy_image *image, const char *filename);
-
 int cammy_image_save(cammy_image *image, const char *filename);
 
-void cammy_image_dither(uint8_t *dest,
-                        uint8_t *src,
-                        size_t width,
-                        size_t height,
-                        int depth,
-                        cammy_tile_palette *palette);
-
 void cammy_image_split_to_tiles(cammy_tile *destr,
                                 cammy_tile *destg,
                                 cammy_tile *destb,
@@ -70,13 +70,6 @@ void cammy_image_split_to_tiles(cammy_tile *destr,
                                 size_t height,
                                 int depth);
 
-void cammy_image_copy_from_tile(uint8_t *dest,
-                                cammy_tile *src,
-                                size_t width,
-                                size_t height,
-                                int depth,
-                                cammy_tile_palette *palette);
-
 void cammy_image_merge_tiles(uint8_t *dest,
                              cammy_tile *srcr,
                              cammy_tile *srcg,

include/cammy/photo.h

@@ -37,9 +37,8 @@ typedef struct _cammy_photo {
 
 #pragma pack(pop)
 
-void cammy_photo_export(cammy_photo *src,
+cammy_image *cammy_photo_export(cammy_photo *src,
-                        uint8_t *dest,
+                                cammy_image_format format,
-                        int depth,
                                 cammy_tile_palette *palette);
 
 void cammy_photo_merge(cammy_photo *srcr,

src/Makefile

@@ -7,12 +7,12 @@ CC		= $(CROSS)cc
 CFLAGS		= $(CGFLAGS) -fPIC -Wall -O2 -I$(INCLUDE_PATH)
 LDFLAGS		= -lz
 
-HEADERS_LOCAL	=
+HEADERS_LOCAL	= pnglite.h
 HEADERS_BUILD	= $(HEADERS_LOCAL) \
 		  $(addprefix $(INCLUDE_PATH)/$(HEADER_SUBDIR)/,$(HEADERS))
 
 HEADERS		= sram.h image.h photo.h
-OBJS		= sram.o image.o photo.o
+OBJS		= sram.o image.o photo.o pnglite.o
 
 VERSION_MAJOR	= 0
 VERSION_MINOR	= 0.1

src/image.c

@@ -10,6 +10,8 @@
 #include <cammy/screen.h>
 #include <cammy/image.h>
 
+#include "pnglite.h"
+
 static uint32_t bayer_matrix[256] = {
     /*
      * Black gamut
@@ -158,8 +160,6 @@ cammy_image *cammy_image_new(cammy_image_format format,
                              size_t width,
                              size_t height) {
     cammy_image *image;
-    uint8_t *buf;
-
     size_t size;
 
     switch (format) {
@@ -188,15 +188,15 @@ cammy_image *cammy_image_new(cammy_image_format format,
         goto error_malloc_image;
     }
 
-    if ((buf = malloc(size)) == NULL) {
+    if ((image->buf = malloc(size)) == NULL) {
         goto error_malloc_buf;
     }
 
-    image->buf    = buf;
     image->format = format;
     image->size   = size;
     image->width  = width;
     image->height = height;
+    image->file   = NULL;
 
     return image;
 
@@ -208,28 +208,84 @@ error_invalid_format:
     return NULL;
 }
 
-void cammy_image_close(cammy_image *image) {
-    free(image);
-}
-
 void cammy_image_destroy(cammy_image *image) {
     free(image->buf);
     free(image);
 }
 
-cammy_image *cammy_image_open_tile(const char *filename,
+static cammy_image *load_png(const char *file) {
-                                   size_t width,
+    png_t png;
-                                   size_t height) {
-    cammy_image *image;
-    int fd;
 
+    cammy_image *image;
+    cammy_image_format format = CAMMY_IMAGE_NONE;
+
+    png_init(malloc, free);
+
+    if (png_open_file_read(&png, file) < 0) {
+        goto error_png_open_file_read;
+    }
+
+    switch (png.bpp) {
+        case 3:
+            format = CAMMY_IMAGE_24BPP_RGB;
+            break;
+
+        case 4:
+            format = CAMMY_IMAGE_32BPP_RGBA;
+            break;
+
+        default:
+            errno = EINVAL;
+            goto error_invalid_format;
+    }
+
+    if ((image = cammy_image_new(format, png.width, png.height)) == NULL) {
+        goto error_image_new;
+    }
+
+    if (png_get_data(&png, image->buf) < 0) {
+        goto error_png_get_data;
+    }
+
+    png_close_file(&png);
+
+    return image;
+
+error_png_get_data:
+    cammy_image_destroy(image);
+
+error_image_new:
+error_invalid_format:
+    png_close_file(&png);
+
+error_png_open_file_read:
+    return NULL;
+}
+
+static cammy_image *load_tile(const char *filename) {
+    int fd;
     size_t off;
 
+    cammy_image *image;
+    cammy_image_header header;
+
     if ((fd = open(filename, O_RDONLY)) < 0) {
         goto error_open;
     }
 
-    if ((image = cammy_image_new(CAMMY_IMAGE_2BPP_TILE, width, height)) == NULL) {
+    if (read(fd, &header, sizeof(header)) < 0) {
+        goto error_read_header;
+    }
+
+    if (be16toh(header.version) != CAMMY_IMAGE_HEADER_VERSION) {
+        errno = EINVAL;
+
+        goto error_invalid_version;
+    }
+
+    if ((image = cammy_image_new(CAMMY_IMAGE_2BPP_TILE,
+                                 be16toh(header.width),
+                                 be16toh(header.height))) == NULL) {
         goto error_image_new;
     }
 
@@ -251,22 +307,81 @@ error_read:
     cammy_image_destroy(image);
 
 error_image_new:
+error_invalid_version:
+error_read_header:
     close(fd);
 
 error_open:
     return NULL;
 }
 
-int cammy_image_save_tile(cammy_image *image, const char *filename) {
+cammy_image *cammy_image_open(const char *file) {
+    cammy_image *image;
+
+    int fd;
+    uint8_t buf[4];
+
+    cammy_image *(*loader)(const char *) = NULL;
+
+    if ((fd = open(file, O_RDONLY)) < 0) {
+        goto error_open;
+    }
+
+    if (lseek(fd, 0, SEEK_SET) < 0) {
+        goto error_lseek;
+    }
+
+    if (read(fd, buf, sizeof(buf)) < 0) {
+        goto error_read;
+    }
+
+    close(fd);
+
+    if (memcmp(buf, CAMMY_IMAGE_MAGIC_PNG, sizeof(buf)) == 0) {
+        loader = load_png;
+    } else if (memcmp(buf, CAMMY_IMAGE_MAGIC_TILE, sizeof(buf)) == 0) {
+        loader = load_tile;
+    } else {
+        goto error_invalid_format;
+    }
+
+    if ((image = loader(file)) == NULL) {
+        goto error_load_image;
+    }
+
+    return image;
+
+error_load_image:
+error_invalid_format:
+error_read:
+error_lseek:
+    close(fd);
+
+error_open:
+    return NULL;
+}
+
+int cammy_image_save(cammy_image *image, const char *filename) {
     size_t off,
            rest = image->size;
 
     int fd;
 
+    cammy_image_header header = {
+        .magic   = CAMMY_IMAGE_MAGIC_TILE,
+        .version = htobe16(CAMMY_IMAGE_HEADER_VERSION),
+        .width   = htobe16(image->width),
+        .height  = htobe16(image->height)
+    };
+
     if ((fd = open(filename, O_CREAT | O_WRONLY | O_TRUNC, 0644)) < 0) {
         goto error_open;
     }
 
+    if (write(fd, &header, sizeof(header)) < 0) {
+        goto error_write;
+    }
+
     for (off=0; off<image->size; off+=CAMMY_IMAGE_CHUNK_SIZE) {
         size_t chunk = rest > CAMMY_IMAGE_CHUNK_SIZE?
                               CAMMY_IMAGE_CHUNK_SIZE: rest;
@@ -532,7 +647,10 @@ int cammy_image_slice(uint8_t *buf,
 
     size_t x, y;
 
-    if ((dest = cammy_image_new(CAMMY_IMAGE_2BPP_TILE, width, height)) == NULL) {
+    if ((dest = cammy_image_new(CAMMY_IMAGE_2BPP_TILE,
+                                width,
+                                height
+                                )) == NULL) {
         goto error_image_new;
     }
 

src/photo.c

@@ -5,10 +5,12 @@
 #include <cammy/image.h>
 #include <cammy/photo.h>
 
-void cammy_photo_export(cammy_photo *src,
+cammy_image *cammy_photo_export(cammy_photo *src,
-                        uint8_t *dest,
+                                cammy_image_format format,
-                        int depth,
                                 cammy_tile_palette *palette) {
+    cammy_image *image;
+
+    if ((image = cammy_image_))
     cammy_image_copy_from_tile(dest,
                                (cammy_tile *)&src->tiles,
                                CAMMY_PHOTO_WIDTH,

src/pnglite.c

@@ -0,0 +1,862 @@
+/*  pnglite.c - pnglite library
+    For conditions of distribution and use, see copyright notice in pnglite.h
+*/
+#define DO_CRC_CHECKS 1
+#define USE_ZLIB 1
+
+#if USE_ZLIB
+#include <zlib.h>
+#else
+#include "zlite.h"
+#endif
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include "pnglite.h"
+
+static png_alloc_t png_alloc;
+static png_free_t png_free;
+
+static size_t file_read(png_t* png, void* out, size_t size, size_t numel)
+{
+	size_t result;
+	if(png->read_fun)
+	{
+		result = png->read_fun(out, size, numel, png->user_pointer);
+	}
+	else
+	{
+		if(!out)
+		{
+			result = fseek(png->user_pointer, (long)(size*numel), SEEK_CUR);
+		}
+		else
+		{
+			result = fread(out, size, numel, png->user_pointer);
+		}
+	}
+
+	return result;
+}
+
+static size_t file_write(png_t* png, void* p, size_t size, size_t numel)
+{
+	size_t result;
+
+	if(png->write_fun)
+	{
+		result = png->write_fun(p, size, numel, png->user_pointer);
+	}
+	else
+	{
+		result = fwrite(p, size, numel, png->user_pointer);
+	}
+
+	return result;
+}
+
+static int file_read_ul(png_t* png, unsigned *out)
+{
+	unsigned char buf[4];
+
+	if(file_read(png, buf, 1, 4) != 4)
+		return PNG_FILE_ERROR;
+
+	*out = (buf[0]<<24) | (buf[1]<<16) | (buf[2]<<8) | buf[3];
+
+	return PNG_NO_ERROR;
+}
+
+static int file_write_ul(png_t* png, unsigned in)
+{
+	unsigned char buf[4];
+
+	buf[0] = (in>>24) & 0xff;
+	buf[1] = (in>>16) & 0xff;
+	buf[2] = (in>>8) & 0xff;
+	buf[3] = (in) & 0xff;
+
+	if(file_write(png, buf, 1, 4) != 4)
+		return PNG_FILE_ERROR;
+
+	return PNG_NO_ERROR;
+}
+
+static unsigned get_ul(unsigned char* buf)
+{
+	unsigned result;
+	unsigned char foo[4];
+
+	memcpy(foo, buf, 4);
+
+	result = (foo[0]<<24) | (foo[1]<<16) | (foo[2]<<8) | foo[3];
+
+	return result;
+}
+
+static unsigned set_ul(unsigned char* buf, unsigned in)
+{
+	buf[0] = (in>>24) & 0xff;
+	buf[1] = (in>>16) & 0xff;
+	buf[2] = (in>>8) & 0xff;
+	buf[3] = (in) & 0xff;
+
+	return PNG_NO_ERROR;
+}
+
+int png_init(png_alloc_t pngalloc, png_free_t pngfree)
+{
+	if(pngalloc)
+		png_alloc = pngalloc;
+	else
+		png_alloc = &malloc;
+
+	if(pngfree)
+		png_free = pngfree;
+	else
+		png_free = &free;
+
+	return PNG_NO_ERROR;
+}
+
+static int png_get_bpp(png_t* png)
+{
+	int bpp;
+
+	switch(png->color_type)
+	{
+	case PNG_GREYSCALE:
+		bpp = 1; break;
+	case PNG_TRUECOLOR:
+		bpp = 3; break;
+	case PNG_INDEXED:
+		bpp = 1; break;
+	case PNG_GREYSCALE_ALPHA:
+		bpp = 2; break;
+	case PNG_TRUECOLOR_ALPHA:
+		bpp = 4; break;
+	default:
+		return PNG_FILE_ERROR;
+	}
+
+	bpp *= png->depth/8;
+
+	return bpp;
+}
+
+static int png_read_ihdr(png_t* png)
+{
+	unsigned length;
+#if DO_CRC_CHECKS
+	unsigned orig_crc;
+	unsigned calc_crc;
+#endif
+	unsigned char ihdr[13+4];		 /* length should be 13, make room for type (IHDR) */
+
+	file_read_ul(png, &length);
+
+	if(length != 13)
+	{
+		printf("%d\n", length);
+		return PNG_CRC_ERROR;
+	}
+
+	if(file_read(png, ihdr, 1, 13+4) != 13+4)
+		return PNG_EOF_ERROR;
+#if DO_CRC_CHECKS
+	file_read_ul(png, &orig_crc);
+
+	calc_crc = crc32(0L, 0, 0);
+	calc_crc = crc32(calc_crc, ihdr, 13+4);
+
+	if(orig_crc != calc_crc)
+		return PNG_CRC_ERROR;
+#else
+	file_read_ul(png);
+#endif
+
+	png->width = get_ul(ihdr+4);
+	png->height = get_ul(ihdr+8);
+	png->depth = ihdr[12];
+	png->color_type = ihdr[13];
+	png->compression_method = ihdr[14];
+	png->filter_method = ihdr[15];
+	png->interlace_method = ihdr[16];
+
+	if(png->color_type == PNG_INDEXED)
+		return PNG_NOT_SUPPORTED;
+
+	if(png->depth != 8 && png->depth != 16)
+		return PNG_NOT_SUPPORTED;
+
+	if(png->interlace_method)
+		return PNG_NOT_SUPPORTED;
+
+	return PNG_NO_ERROR;
+}
+
+static int png_write_ihdr(png_t* png)
+{
+	unsigned char ihdr[13+4];
+	unsigned char *p = ihdr;
+	unsigned crc;
+
+	file_write(png, "\x89\x50\x4E\x47\x0D\x0A\x1A\x0A", 1, 8);
+
+	file_write_ul(png, 13);
+
+	*p = 'I';			p++;
+	*p = 'H';			p++;
+	*p = 'D';			p++;
+	*p = 'R';			p++;
+	set_ul(p, png->width);		p+=4;
+	set_ul(p, png->height);		p+=4;
+	*p = png->depth;		p++;
+	*p = png->color_type;		p++;
+	*p = 0;				p++;
+	*p = 0;				p++;
+	*p = 0;				p++;
+
+	file_write(png, ihdr, 1, 13+4);
+
+	crc = crc32(0L, 0, 0);
+	crc = crc32(crc, ihdr, 13+4);
+
+	file_write_ul(png, crc);
+
+	return PNG_NO_ERROR;
+}
+
+void png_print_info(png_t* png)
+{
+	printf("PNG INFO:\n");
+	printf("\twidth:\t\t%d\n", png->width);
+	printf("\theight:\t\t%d\n", png->height);
+	printf("\tdepth:\t\t%d\n", png->depth);
+	printf("\tcolor:\t\t");
+
+	switch(png->color_type)
+	{
+	case PNG_GREYSCALE:		printf("greyscale\n"); break;
+	case PNG_TRUECOLOR:		printf("truecolor\n"); break;
+	case PNG_INDEXED:		printf("palette\n"); break;
+	case PNG_GREYSCALE_ALPHA:	printf("greyscale with alpha\n"); break;
+	case PNG_TRUECOLOR_ALPHA:	printf("truecolor with alpha\n"); break;
+	default:			printf("unknown, this is not good\n"); break;
+	}
+
+	printf("\tcompression:\t%s\n",	png->compression_method?"unknown, this is not good":"inflate/deflate");
+	printf("\tfilter:\t\t%s\n",	png->filter_method?"unknown, this is not good":"adaptive");
+	printf("\tinterlace:\t%s\n",	png->interlace_method?"interlace":"no interlace");
+}
+
+int png_open_read(png_t* png, png_read_callback_t read_fun, void* user_pointer)
+{
+	char header[8];
+	int result;
+
+	png->read_fun = read_fun;
+	png->write_fun = 0;
+	png->user_pointer = user_pointer;
+
+	if(!read_fun && !user_pointer)
+		return PNG_WRONG_ARGUMENTS;
+
+	if(file_read(png, header, 1, 8) != 8)
+		return PNG_EOF_ERROR;
+
+	if(memcmp(header, "\x89\x50\x4E\x47\x0D\x0A\x1A\x0A", 8) != 0)
+		return PNG_HEADER_ERROR;
+
+	result = png_read_ihdr(png);
+
+	png->bpp = (unsigned char)png_get_bpp(png);
+
+	return result;
+}
+
+int png_open_write(png_t* png, png_write_callback_t write_fun, void* user_pointer)
+{
+	png->write_fun = write_fun;
+	png->read_fun = 0;
+	png->user_pointer = user_pointer;
+
+	if(!write_fun && !user_pointer)
+		return PNG_WRONG_ARGUMENTS;
+
+	return PNG_NO_ERROR;
+}
+
+int png_open(png_t* png, png_read_callback_t read_fun, void* user_pointer)
+{
+	return png_open_read(png, read_fun, user_pointer);
+}
+
+int png_open_file_read(png_t *png, const char* filename)
+{
+	FILE* fp = fopen(filename, "rb");
+
+	if(!fp)
+		return PNG_FILE_ERROR;
+
+	return png_open_read(png, 0, fp);
+}
+
+int png_open_file_write(png_t *png, const char* filename)
+{
+	FILE* fp = fopen(filename, "wb");
+
+	if(!fp)
+		return PNG_FILE_ERROR;
+
+	return png_open_write(png, 0, fp);
+}
+
+int png_open_file(png_t *png, const char* filename)
+{
+	return png_open_file_read(png, filename);
+}
+
+int png_close_file(png_t* png)
+{
+	fclose(png->user_pointer);
+
+	return PNG_NO_ERROR;
+}
+
+static int png_init_deflate(png_t* png, unsigned char* data, int datalen)
+{
+	z_stream *stream;
+	png->zs = png_alloc(sizeof(z_stream));
+
+	stream = png->zs;
+
+	if(!stream)
+		return PNG_MEMORY_ERROR;
+
+	memset(stream, 0, sizeof(z_stream));
+
+	if(deflateInit(stream, Z_DEFAULT_COMPRESSION) != Z_OK)
+		return PNG_ZLIB_ERROR;
+
+	stream->next_in = data;
+	stream->avail_in = datalen;
+
+	return PNG_NO_ERROR;
+}
+
+static int png_init_inflate(png_t* png)
+{
+#if USE_ZLIB
+	z_stream *stream;
+	png->zs = png_alloc(sizeof(z_stream));
+#else
+	zl_stream *stream;
+	png->zs = png_alloc(sizeof(zl_stream));
+#endif
+
+	stream = png->zs;
+
+	if(!stream)
+		return PNG_MEMORY_ERROR;
+
+#if USE_ZLIB
+	memset(stream, 0, sizeof(z_stream));
+	if(inflateInit(stream) != Z_OK)
+		return PNG_ZLIB_ERROR;
+#else
+	memset(stream, 0, sizeof(zl_stream));
+	if(z_inflateInit(stream) != Z_OK)
+		return PNG_ZLIB_ERROR;
+#endif
+
+	stream->next_out = png->png_data;
+	stream->avail_out = png->png_datalen;
+
+	return PNG_NO_ERROR;
+}
+
+static int png_end_deflate(png_t* png)
+{
+	z_stream *stream = png->zs;
+
+	if(!stream)
+		return PNG_MEMORY_ERROR;
+
+	deflateEnd(stream);
+
+	png_free(png->zs);
+
+	return PNG_NO_ERROR;
+}
+
+static int png_end_inflate(png_t* png)
+{
+#if USE_ZLIB
+	z_stream *stream = png->zs;
+#else
+	zl_stream *stream = png->zs;
+#endif
+
+	if(!stream)
+		return PNG_MEMORY_ERROR;
+
+#if USE_ZLIB
+	if(inflateEnd(stream) != Z_OK)
+#else
+	if(z_inflateEnd(stream) != Z_OK)
+#endif
+	{
+		printf("ZLIB says: %s\n", stream->msg);
+		return PNG_ZLIB_ERROR;
+	}
+
+	png_free(png->zs);
+
+	return PNG_NO_ERROR;
+}
+
+static int png_inflate(png_t* png, unsigned char* data, int len)
+{
+	int result;
+#if USE_ZLIB
+	z_stream *stream = png->zs;
+#else
+	zl_stream *stream = png->zs;
+#endif
+
+	if(!stream)
+		return PNG_MEMORY_ERROR;
+
+	stream->next_in = data;
+	stream->avail_in = len;
+
+#if USE_ZLIB
+	result = inflate(stream, Z_SYNC_FLUSH);
+#else
+	result = z_inflate(stream);
+#endif
+
+	if(result != Z_STREAM_END && result != Z_OK)
+	{
+		printf("%s\n", stream->msg);
+		return PNG_ZLIB_ERROR;
+	}
+
+	if(stream->avail_in != 0)
+		return PNG_ZLIB_ERROR;
+
+	return PNG_NO_ERROR;
+}
+
+static int png_deflate(png_t* png, char* outdata, int outlen, int *outwritten)
+{
+	int result;
+
+	z_stream *stream = png->zs;
+
+	if(!stream)
+		return PNG_MEMORY_ERROR;
+
+	stream->next_out = (unsigned char*)outdata;
+	stream->avail_out = outlen;
+
+	result = deflate(stream, Z_SYNC_FLUSH);
+
+	*outwritten = outlen - stream->avail_out;
+
+	if(result != Z_STREAM_END && result != Z_OK)
+	{
+		printf("%s\n", stream->msg);
+		return PNG_ZLIB_ERROR;
+	}
+
+	return result;
+}
+
+static int png_write_idats(png_t* png, unsigned char* data)
+{
+	unsigned char *chunk;
+	unsigned long written;
+	unsigned long crc;
+	unsigned size = png->width * png->height * png->bpp + png->height;
+	unsigned chunk_size = compressBound(size);
+
+	(void)png_init_deflate;
+	(void)png_end_deflate;
+	(void)png_deflate;
+
+	chunk = png_alloc(chunk_size + 4);
+	memcpy(chunk, "IDAT", 4);
+
+	written = chunk_size;
+	compress(chunk+4, &written, data, size);
+
+	crc = crc32(0L, Z_NULL, 0);
+	crc = crc32(crc, chunk, written+4);
+	set_ul(chunk+written+4, crc);
+	file_write_ul(png, written);
+	file_write(png, chunk, 1, written+8);
+	png_free(chunk);
+
+	file_write_ul(png, 0);
+	file_write(png, "IEND", 1, 4);
+	crc = crc32(0L, (const unsigned char *)"IEND", 4);
+	file_write_ul(png, crc);
+
+	return PNG_NO_ERROR;
+}
+
+static int png_read_idat(png_t* png, unsigned length)
+{
+#if DO_CRC_CHECKS
+	unsigned orig_crc;
+	unsigned calc_crc;
+#endif
+
+	if(!png->readbuf || png->readbuflen < length)
+	{
+		if (png->readbuf)
+		{
+			png_free(png->readbuf);
+		}
+		png->readbuf = png_alloc(length);
+		png->readbuflen = length;
+	}
+
+	if(!png->readbuf)
+	{
+		return PNG_MEMORY_ERROR;
+	}
+
+	if(file_read(png, png->readbuf, 1, length) != length)
+	{
+		return PNG_FILE_ERROR;
+	}
+
+#if DO_CRC_CHECKS
+	calc_crc = crc32(0L, Z_NULL, 0);
+	calc_crc = crc32(calc_crc, (unsigned char*)"IDAT", 4);
+	calc_crc = crc32(calc_crc, (unsigned char*)png->readbuf, length);
+
+	file_read_ul(png, &orig_crc);
+
+	if(orig_crc != calc_crc)
+	{
+		return PNG_CRC_ERROR;
+	}
+#else
+	file_read_ul(png);
+#endif
+
+	return png_inflate(png, png->readbuf, length);
+}
+
+static int png_process_chunk(png_t* png)
+{
+	int result = PNG_NO_ERROR;
+	unsigned type;
+	unsigned length;
+
+	file_read_ul(png, &length);
+
+	if(file_read(png, &type, 1, 4) != 4)
+		return PNG_FILE_ERROR;
+
+	if(type == *(unsigned int*)"IDAT")	/* if we found an idat, all other idats should be followed with no other chunks in between */
+	{
+		if(!png->png_data) /* first IDAT */
+		{
+			png->png_datalen = png->width * png->height * png->bpp + png->height;
+			png->png_data = png_alloc(png->png_datalen);
+		}
+
+		if(!png->png_data)
+			return PNG_MEMORY_ERROR;
+
+		if(!png->zs)
+		{
+			result = png_init_inflate(png);
+			if(result != PNG_NO_ERROR)
+				return result;
+		}
+
+		return png_read_idat(png, length);
+	}
+	else if(type == *(unsigned int*)"IEND")
+	{
+		return PNG_DONE;
+	}
+	else
+	{
+		file_read(png, 0, 1, length + 4); /* unknown chunk */
+	}
+
+	return result;
+}
+
+static void png_filter_sub(int stride, unsigned char* in, unsigned char* out, int len)
+{
+	int i;
+	unsigned char a = 0;
+
+	for(i = 0; i < len; i++)
+	{
+		if(i >= stride)
+			a = out[i - stride];
+
+		out[i] = in[i] + a;
+	}
+}
+
+static void png_filter_up(int stride, unsigned char* in, unsigned char* out, unsigned char* prev_line, int len)
+{
+	int i;
+
+	if(prev_line)
+	{
+        for(i = 0; i < len; i++)
+		out[i] = in[i] + prev_line[i];
+	}
+	else
+		memcpy(out, in, len);
+}
+
+static void png_filter_average(int stride, unsigned char* in, unsigned char* out, unsigned char* prev_line, int len)
+{
+	int i;
+	unsigned char a = 0;
+	unsigned char b = 0;
+	unsigned int sum = 0;
+
+	for(i = 0; i < len; i++)
+	{
+		if(prev_line)
+			b = prev_line[i];
+
+		if(i >= stride)
+			a = out[i - stride];
+
+		sum = a;
+		sum += b;
+
+		out[i] = (char)(in[i] + sum/2);
+	}
+}
+
+static unsigned char png_paeth(unsigned char a, unsigned char b, unsigned char c)
+{
+	int p = (int)a + b - c;
+	int pa = abs(p - a);
+	int pb = abs(p - b);
+	int pc = abs(p - c);
+
+	int pr;
+
+	if(pa <= pb && pa <= pc)
+		pr = a;
+	else if(pb <= pc)
+		pr = b;
+	else
+		pr = c;
+
+	return (char)pr;
+}
+
+static void png_filter_paeth(int stride, unsigned char* in, unsigned char* out, unsigned char* prev_line, int len)
+{
+	int i;
+	unsigned char a;
+	unsigned char b;
+	unsigned char c;
+
+	for(i = 0; i < len; i++)
+	{
+		if(prev_line && i >= stride)
+		{
+			a = out[i - stride];
+			b = prev_line[i];
+			c = prev_line[i - stride];
+		}
+		else
+		{
+			if(prev_line)
+				b = prev_line[i];
+			else
+				b = 0;
+
+			if(i >= stride)
+				a = out[i - stride];
+			else
+				a = 0;
+
+			c = 0;
+		}
+
+		out[i] = in[i] + png_paeth(a, b, c);
+	}
+}
+
+static int png_filter(png_t* png, unsigned char* data)
+{
+	return PNG_NO_ERROR;
+}
+
+static int png_unfilter(png_t* png, unsigned char* data)
+{
+	unsigned i;
+	unsigned pos = 0;
+	unsigned outpos = 0;
+	unsigned char *filtered = png->png_data;
+
+	int stride = png->bpp;
+
+	while(pos < png->png_datalen)
+	{
+		unsigned char filter = filtered[pos];
+
+		pos++;
+
+		if(png->depth == 16)
+		{
+			for(i = 0; i < png->width * stride; i+=2)
+			{
+				*(short*)(filtered+pos+i) = (filtered[pos+i] << 8) | filtered[pos+i+1];
+			}
+		}
+
+		switch(filter)
+		{
+		case 0: /* none */
+			memcpy(data+outpos, filtered+pos, png->width * stride);
+			break;
+		case 1: /* sub */
+			png_filter_sub(stride, filtered+pos, data+outpos, png->width * stride);
+			break;
+		case 2: /* up */
+			if(outpos)
+				png_filter_up(stride, filtered+pos, data+outpos, data + outpos - (png->width*stride), png->width*stride);
+			else
+				png_filter_up(stride, filtered+pos, data+outpos, 0, png->width*stride);
+			break;
+		case 3: /* average */
+			if(outpos)
+				png_filter_average(stride, filtered+pos, data+outpos, data + outpos - (png->width*stride), png->width*stride);
+			else
+				png_filter_average(stride, filtered+pos, data+outpos, 0, png->width*stride);
+			break;
+		case 4: /* paeth */
+			if(outpos)
+				png_filter_paeth(stride, filtered+pos, data+outpos, data + outpos - (png->width*stride), png->width*stride);
+			else
+				png_filter_paeth(stride, filtered+pos, data+outpos, 0, png->width*stride);
+			break;
+		default:
+			return PNG_UNKNOWN_FILTER;
+		}
+
+		outpos += png->width * stride;
+		pos += png->width * stride;
+	}
+
+	return PNG_NO_ERROR;
+}
+
+int png_get_data(png_t* png, unsigned char* data)
+{
+	int result = PNG_NO_ERROR;
+
+	png->zs = NULL;
+	png->png_datalen = 0;
+	png->png_data = NULL;
+	png->readbuf = NULL;
+	png->readbuflen = 0;
+
+	while(result == PNG_NO_ERROR)
+	{
+		result = png_process_chunk(png);
+	}
+
+	if (png->readbuf)
+	{
+		png_free(png->readbuf);
+		png->readbuflen = 0;
+	}
+	if (png->zs)
+	{
+		png_end_inflate(png);
+	}
+
+	if(result != PNG_DONE)
+	{
+		png_free(png->png_data);
+		return result;
+	}
+
+	result = png_unfilter(png, data);
+
+	png_free(png->png_data);
+
+	return result;
+}
+
+int png_set_data(png_t* png, unsigned width, unsigned height, char depth, int color, unsigned char* data)
+{
+	int i;
+	unsigned char *filtered;
+	png->width = width;
+	png->height = height;
+	png->depth = depth;
+	png->color_type = color;
+	png->bpp = png_get_bpp(png);
+
+	filtered = png_alloc(width * height * png->bpp + height);
+
+	for(i = 0; i < png->height; i++)
+	{
+		filtered[i*png->width*png->bpp+i] = 0;
+		memcpy(&filtered[i*png->width*png->bpp+i+1], data + i * png->width*png->bpp, png->width*png->bpp);
+	}
+
+	png_filter(png, filtered);
+	png_write_ihdr(png);
+	png_write_idats(png, filtered);
+
+	png_free(filtered);
+
+	return PNG_NO_ERROR;
+}
+
+char* png_error_string(int error)
+{
+	switch(error)
+	{
+	case PNG_NO_ERROR:
+		return "No error";
+	case PNG_FILE_ERROR:
+		return "Unknown file error.";
+	case PNG_HEADER_ERROR:
+		return "No PNG header found. Are you sure this is a PNG?";
+	case PNG_IO_ERROR:
+		return "Failure while reading file.";
+	case PNG_EOF_ERROR:
+		return "Reached end of file.";
+	case PNG_CRC_ERROR:
+		return "CRC or chunk length error.";
+	case PNG_MEMORY_ERROR:
+		return "Could not allocate memory.";
+	case PNG_ZLIB_ERROR:
+		return "zlib reported an error.";
+	case PNG_UNKNOWN_FILTER:
+		return "Unknown filter method used in scanline.";
+	case PNG_DONE:
+		return "PNG done";
+	case PNG_NOT_SUPPORTED:
+		return "The PNG is unsupported by pnglite, too bad for you!";
+	case PNG_WRONG_ARGUMENTS:
+		return "Wrong combination of arguments passed to png_open. You must use either a read_function or supply a file pointer to use.";
+	default:
+		return "Unknown error.";
+	};
+}

src/pnglite.h

@@ -0,0 +1,232 @@
+/*  pnglite.h - Interface for pnglite library
+	Copyright (c) 2007 Daniel Karling
+
+	This software is provided 'as-is', without any express or implied
+	warranty. In no event will the authors be held liable for any damages
+	arising from the use of this software.
+
+	Permission is granted to anyone to use this software for any purpose,
+	including commercial applications, and to alter it and redistribute it
+	freely, subject to the following restrictions:
+
+	1. The origin of this software must not be misrepresented; you must not
+	   claim that you wrote the original software. If you use this software
+	   in a product, an acknowledgment in the product documentation would be
+	   appreciated but is not required.
+
+	2. Altered source versions must be plainly marked as such, and must not be
+	   misrepresented as being the original software.
+
+	3. This notice may not be removed or altered from any source
+	   distribution.
+
+	Daniel Karling
+	daniel.karling@gmail.com
+ */
+
+
+#ifndef _PNGLITE_H_
+#define _PNGLITE_H_
+
+#include <string.h>
+
+#ifdef __cplusplus
+extern "C"{
+#endif
+
+/*
+	Enumerations for pnglite.
+	Negative numbers are error codes and 0 and up are okay responses.
+*/
+
+enum
+{
+	PNG_DONE			= 1,
+	PNG_NO_ERROR			= 0,
+	PNG_FILE_ERROR			= -1,
+	PNG_HEADER_ERROR		= -2,
+	PNG_IO_ERROR			= -3,
+	PNG_EOF_ERROR			= -4,
+	PNG_CRC_ERROR			= -5,
+	PNG_MEMORY_ERROR		= -6,
+	PNG_ZLIB_ERROR			= -7,
+	PNG_UNKNOWN_FILTER		= -8,
+	PNG_NOT_SUPPORTED		= -9,
+	PNG_WRONG_ARGUMENTS		= -10
+};
+
+/*
+	The five different kinds of color storage in PNG files.
+*/
+
+enum
+{
+	PNG_GREYSCALE			= 0,
+	PNG_TRUECOLOR			= 2,
+	PNG_INDEXED			= 3,
+	PNG_GREYSCALE_ALPHA		= 4,
+	PNG_TRUECOLOR_ALPHA		= 6
+};
+
+/*
+	Typedefs for callbacks.
+*/
+
+typedef unsigned (*png_write_callback_t)(void* input, size_t size, size_t numel, void* user_pointer);
+typedef unsigned (*png_read_callback_t)(void* output, size_t size, size_t numel, void* user_pointer);
+typedef void (*png_free_t)(void* p);
+typedef void * (*png_alloc_t)(size_t s);
+
+typedef struct
+{
+	void*				zs;				/* pointer to z_stream */
+	png_read_callback_t		read_fun;
+	png_write_callback_t		write_fun;
+	void*				user_pointer;
+
+	unsigned char*			png_data;
+	unsigned			png_datalen;
+
+	unsigned			width;
+	unsigned			height;
+	unsigned char			depth;
+	unsigned char			color_type;
+	unsigned char			compression_method;
+	unsigned char			filter_method;
+	unsigned char			interlace_method;
+	unsigned char			bpp;
+
+	unsigned char*			readbuf;
+	unsigned			readbuflen;
+} png_t;
+
+/*
+	Function: png_init
+
+	This function initializes pnglite. The parameters can be used to set your own memory allocation routines following these formats:
+
+	> void* (*custom_alloc)(size_t s)
+	> void (*custom_free)(void* p)
+	Parameters:
+		pngalloc - Pointer to custom allocation routine. If 0 is passed, malloc from libc will be used.
+		pngfree - Pointer to custom free routine. If 0 is passed, free from libc will be used.
+
+	Returns:
+		Always returns PNG_NO_ERROR.
+*/
+
+int png_init(png_alloc_t pngalloc, png_free_t pngfree);
+
+/*
+	Function: png_open_file
+
+	This function is used to open a png file with the internal file IO system. This function should be used instead of
+	png_open if no custom read function is used.
+
+	Parameters:
+		png - Empty png_t struct.
+		filename - Filename of the file to be opened.
+
+	Returns:
+		PNG_NO_ERROR on success, otherwise an error code.
+*/
+
+int png_open_file(png_t *png, const char* filename);
+
+int png_open_file_read(png_t *png, const char* filename);
+int png_open_file_write(png_t *png, const char* filename);
+
+/*
+	Function: png_open
+
+	This function reads or writes a png from/to the specified callback. The callbacks should be of the format:
+
+	> size_t (*png_write_callback_t)(void* input, size_t size, size_t numel, void* user_pointer);
+	> size_t (*png_read_callback_t)(void* output, size_t size, size_t numel, void* user_pointer).
+
+	Only one callback has to be specified. The read callback in case of PNG reading, otherwise the write callback.
+
+	Writing:
+	The callback will be called like fwrite.
+
+	Reading:
+	The callback will be called each time pnglite needs more data. The callback should read as much data as requested,
+	or return 0. This should always be possible if the PNG is sane.	If the output-buffer is a null-pointer the callback
+	should only skip ahead the specified number of elements. If the callback is a null-pointer the user_pointer will be
+	treated as a file pointer (use png_open_file instead).
+
+	Parameters:
+		png - png_t struct
+		read_fun - Callback function for reading.
+		user_pointer - User pointer to be passed to read_fun.
+
+	Returns:
+		PNG_NO_ERROR on success, otherwise an error code.
+*/
+
+int png_open(png_t* png, png_read_callback_t read_fun, void* user_pointer);
+
+int png_open_read(png_t* png, png_read_callback_t read_fun, void* user_pointer);
+int png_open_write(png_t* png, png_write_callback_t write_fun, void* user_pointer);
+
+/*
+	Function: png_print_info
+
+	This function prints some info about the opened png file to stdout.
+
+	Parameters:
+		png - png struct to get info from.
+*/
+
+void png_print_info(png_t* png);
+
+/*
+	Function: png_error_string
+
+	This function translates an error code to a human readable string.
+
+	Parameters:
+		error - Error code.
+
+	Returns:
+		Pointer to string.
+*/
+
+char* png_error_string(int error);
+
+/*
+	Function: png_get_data
+
+	This function decodes the opened png file and stores the result in data. data should be big enough to hold the decoded png. Required size will be:
+
+	> width*height*(bytes per pixel)
+
+	Parameters:
+		data - Where to store result.
+
+	Returns:
+		PNG_NO_ERROR on success, otherwise an error code.
+*/
+
+int png_get_data(png_t* png, unsigned char* data);
+
+int png_set_data(png_t* png, unsigned width, unsigned height, char depth, int color, unsigned char* data);
+
+/*
+	Function: png_close_file
+
+	Closes an open png file pointer. Should only be used when the png has been opened with png_open_file.
+
+	Parameters:
+		png - png to close.
+
+	Returns:
+		PNG_NO_ERROR
+*/
+
+int png_close_file(png_t* png);
+
+#ifdef __cplusplus
+}
+#endif
+#endif