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/* loadpng, Allegro wrapper routines for libpng
* by Peter Wang (tjaden@users.sf.net).
*
* This file is hereby placed in the public domain.
*/
#include <zlib.h>
#include <png.h>
#include <allegro.h>
#include <allegro/internal/aintern.h>
#include "loadpng.h"
/* We need internals _color_load_depth and _fixup_loaded_bitmap. The
* first can be replaced by the new get_color_depth() function which
* is in Allegro 4.1 branch. But it's not worth it to break 4.0
* compatibility.
*/
double _png_screen_gamma = -1.0;
int _png_compression_level = Z_BEST_COMPRESSION;
/* get_gamma:
* Get screen gamma value one of three ways.
*/
static double get_gamma(void)
{
if (_png_screen_gamma == -1.0) {
/* Use the environment variable if available.
* 2.2 is a good guess for PC monitors.
* 1.1 is good for my laptop.
*/
AL_CONST char *gamma_str = getenv("SCREEN_GAMMA");
return (gamma_str) ? atof(gamma_str) : 2.2;
}
return _png_screen_gamma;
}
/* read_data:
* Custom read function to use Allegro packfile routines,
* rather than C streams (so we can read from datafiles!)
*/
static void read_data(png_structp png_ptr, png_bytep data, png_uint_32 length)
{
PACKFILE *f = (PACKFILE *)png_get_io_ptr(png_ptr);
if ((png_uint_32)pack_fread(data, length, f) != length)
png_error(png_ptr, "read error (loadpng calling pack_fread)");
}
/* check_if_png:
* Check if input file is really PNG format.
*/
#define PNG_BYTES_TO_CHECK 4
static int check_if_png(PACKFILE *fp)
{
char buf[PNG_BYTES_TO_CHECK];
ASSERT(fp);
if (pack_fread(buf, PNG_BYTES_TO_CHECK, fp) != PNG_BYTES_TO_CHECK)
return 0;
return (png_sig_cmp((png_byte *)buf, (png_size_t)0, PNG_BYTES_TO_CHECK) == 0);
}
/* really_load_png:
* Worker routine, used by load_png and load_memory_png.
*/
static BITMAP *really_load_png(png_structp png_ptr, png_infop info_ptr, RGB *pal)
{
BITMAP *bmp;
PALETTE tmppal;
png_uint_32 width, height, rowbytes;
int bit_depth, color_type, interlace_type;
double image_gamma, screen_gamma;
int intent;
int bpp, dest_bpp;
int tRNS_to_alpha = FALSE;
int number_passes, pass;
ASSERT(png_ptr && info_ptr && rgb);
/* The call to png_read_info() gives us all of the information from the
* PNG file before the first IDAT (image data chunk).
*/
png_read_info(png_ptr, info_ptr);
png_get_IHDR(png_ptr, info_ptr, &width, &height, &bit_depth, &color_type,
&interlace_type, NULL, NULL);
/* Extract multiple pixels with bit depths of 1, 2, and 4 from a single
* byte into separate bytes (useful for paletted and grayscale images).
*/
png_set_packing(png_ptr);
/* Expand grayscale images to the full 8 bits from 1, 2, or 4 bits/pixel */
if ((color_type == PNG_COLOR_TYPE_GRAY) && (bit_depth < 8))
png_set_expand(png_ptr);
/* Adds a full alpha channel if there is transparency information
* in a tRNS chunk. */
if (png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS)) {
png_set_tRNS_to_alpha(png_ptr);
tRNS_to_alpha = TRUE;
}
/* Convert 16-bits per colour component to 8-bits per colour component. */
if (bit_depth == 16)
png_set_strip_16(png_ptr);
/* Convert grayscale to RGB triplets */
if ((color_type == PNG_COLOR_TYPE_GRAY) ||
(color_type == PNG_COLOR_TYPE_GRAY_ALPHA))
png_set_gray_to_rgb(png_ptr);
/* Optionally, tell libpng to handle the gamma correction for us. */
if (_png_screen_gamma != 0.0) {
screen_gamma = get_gamma();
if (png_get_sRGB(png_ptr, info_ptr, &intent))
png_set_gamma(png_ptr, screen_gamma, 0.45455);
else {
if (png_get_gAMA(png_ptr, info_ptr, &image_gamma))
png_set_gamma(png_ptr, screen_gamma, image_gamma);
else
png_set_gamma(png_ptr, screen_gamma, 0.45455);
}
}
/* Turn on interlace handling. */
number_passes = png_set_interlace_handling(png_ptr);
/* Call to gamma correct and add the background to the palette
* and update info structure.
*/
png_read_update_info(png_ptr, info_ptr);
/* Even if the user doesn't supply space for a palette, we want
* one for the load process.
*/
if (!pal)
pal = tmppal;
/* Palettes. */
if (color_type & PNG_COLOR_MASK_PALETTE) {
int num_palette, i;
png_colorp palette;
if (png_get_PLTE(png_ptr, info_ptr, &palette, &num_palette)) {
/* We don't actually dither, we just copy the palette. */
for (i = 0; ((i < num_palette) && (i < 256)); i++) {
pal[i].r = palette[i].red >> 2; /* 256 -> 64 */
pal[i].g = palette[i].green >> 2;
pal[i].b = palette[i].blue >> 2;
}
for (; i < 256; i++)
pal[i].r = pal[i].g = pal[i].b = 0;
}
}
else {
generate_332_palette(pal);
}
rowbytes = png_get_rowbytes(png_ptr, info_ptr);
/* Allocate the memory to hold the image using the fields of info_ptr. */
bpp = rowbytes * 8 / width;
/* Allegro cannot handle less than 8 bpp. */
if (bpp < 8)
bpp = 8;
dest_bpp = _color_load_depth(bpp, (bpp == 32));
bmp = create_bitmap_ex(bpp, width, height);
/* Maybe flip RGB to BGR. */
if ((bpp == 24) || (bpp == 32)) {
int c = makecol_depth(bpp, 0, 0, 255);
unsigned char *pc = (unsigned char *)&c;
if (pc[0] == 255)
png_set_bgr(png_ptr);
}
/* Read the image, one line at a line (easier to debug!) */
for (pass = 0; pass < number_passes; pass++) {
png_uint_32 y;
for (y = 0; y < height; y++)
png_read_row(png_ptr, bmp->line[y], NULL);
}
/* Let Allegro convert the image into the desired colour depth. */
if (dest_bpp != bpp)
bmp = _fixup_loaded_bitmap(bmp, pal, dest_bpp);
/* Read rest of file, and get additional chunks in info_ptr. */
png_read_end(png_ptr, info_ptr);
return bmp;
}
/* load_png:
* Load a PNG file from disk, doing colour coversion if required.
*/
BITMAP *load_png(AL_CONST char *filename, RGB *pal)
{
PACKFILE *fp;
BITMAP *bmp;
png_structp png_ptr;
png_infop info_ptr;
ASSERT(filename);
fp = pack_fopen(filename, "r");
if (!fp)
return NULL;
if (!check_if_png(fp)) {
pack_fclose(fp);
return NULL;
}
/* Create and initialize the png_struct with the desired error handler
* functions. If you want to use the default stderr and longjump method,
* you can supply NULL for the last three parameters. We also supply the
* the compiler header file version, so that we know if the application
* was compiled with a compatible version of the library.
*/
png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING,
(void *)NULL, NULL, NULL);
if (!png_ptr) {
pack_fclose(fp);
return NULL;
}
/* Allocate/initialize the memory for image information. */
info_ptr = png_create_info_struct(png_ptr);
if (!info_ptr) {
png_destroy_read_struct(&png_ptr, (png_infopp)NULL, (png_infopp)NULL);
pack_fclose(fp);
return NULL;
}
/* Set error handling if you are using the setjmp/longjmp method (this is
* the normal method of doing things with libpng). REQUIRED unless you
* set up your own error handlers in the png_create_read_struct() earlier.
*/
if (setjmp(png_jmpbuf(png_ptr))) {
/* Free all of the memory associated with the png_ptr and info_ptr */
png_destroy_read_struct(&png_ptr, &info_ptr, (png_infopp)NULL);
pack_fclose(fp);
/* If we get here, we had a problem reading the file */
return NULL;
}
/* Use Allegro packfile routines. */
png_set_read_fn(png_ptr, fp, (png_rw_ptr)read_data);
/* We have already read some of the signature. */
png_set_sig_bytes(png_ptr, PNG_BYTES_TO_CHECK);
/* Really load the image now. */
bmp = really_load_png(png_ptr, info_ptr, pal);
/* Clean up after the read, and free any memory allocated. */
png_destroy_read_struct(&png_ptr, &info_ptr, (png_infopp)NULL);
/* Done. */
pack_fclose(fp);
return bmp;
}
/* read_data_memory:
* Custom reader function to read a PNG file from a memory buffer.
*/
typedef struct {
AL_CONST char *buffer;
png_uint_32 bufsize;
png_uint_32 current_pos;
} MEMORY_READER_STATE;
static void read_data_memory(png_structp png_ptr, png_bytep data, png_uint_32 length)
{
MEMORY_READER_STATE *f = (MEMORY_READER_STATE *)png_get_io_ptr(png_ptr);
if (length > (f->bufsize - f->current_pos))
png_error(png_ptr, "read error in read_data_memory (loadpng)");
memcpy(data, f->buffer + f->current_pos, length);
f->current_pos += length;
}
/* check_if_png_memory:
* Check if input buffer is really PNG format.
*/
static int check_if_png_memory(AL_CONST void *buffer)
{
return (png_sig_cmp((png_byte *)buffer, (png_size_t)0, PNG_BYTES_TO_CHECK) == 0);
}
/* load_memory_png:
* Load a PNG file from memory, doing colour coversion if required.
*/
BITMAP *load_memory_png(AL_CONST void *buffer, int bufsize, RGB *pal)
{
MEMORY_READER_STATE memory_reader_state;
BITMAP *bmp;
png_structp png_ptr;
png_infop info_ptr;
if (!buffer || (bufsize <= 0))
return NULL;
if (!check_if_png_memory(buffer))
return NULL;
/* Create and initialize the png_struct with the desired error handler
* functions. If you want to use the default stderr and longjump method,
* you can supply NULL for the last three parameters. We also supply the
* the compiler header file version, so that we know if the application
* was compiled with a compatible version of the library.
*/
png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING,
(void *)NULL, NULL, NULL);
if (!png_ptr)
return NULL;
/* Allocate/initialize the memory for image information. */
info_ptr = png_create_info_struct(png_ptr);
if (!info_ptr) {
png_destroy_read_struct(&png_ptr, (png_infopp)NULL, (png_infopp)NULL);
return NULL;
}
/* Set error handling if you are using the setjmp/longjmp method (this is
* the normal method of doing things with libpng). REQUIRED unless you
* set up your own error handlers in the png_create_read_struct() earlier.
*/
if (setjmp(png_jmpbuf(png_ptr))) {
/* Free all of the memory associated with the png_ptr and info_ptr */
png_destroy_read_struct(&png_ptr, &info_ptr, (png_infopp)NULL);
/* If we get here, we had a problem reading the file */
return NULL;
}
/* Set up the reader state. */
memory_reader_state.buffer = (const char *)buffer;
memory_reader_state.bufsize = bufsize;
memory_reader_state.current_pos = PNG_BYTES_TO_CHECK;
/* Tell libpng to use our custom reader. */
png_set_read_fn(png_ptr, &memory_reader_state, (png_rw_ptr)read_data_memory);
/* We have already read some of the signature. */
png_set_sig_bytes(png_ptr, PNG_BYTES_TO_CHECK);
/* Really load the image now. */
bmp = really_load_png(png_ptr, info_ptr, pal);
/* Clean up after the read, and free any memory allocated. */
png_destroy_read_struct(&png_ptr, &info_ptr, (png_infopp)NULL);
return bmp;
}
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