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Initial implementation draft
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@Starbuck5
Starbuck5 committed Aug 5, 2024
1 parent 4ce3f94 commit 1f99dfa
Showing 1 changed file with 135 additions and 2 deletions.
137 changes: 135 additions & 2 deletions src/IMG_png.c
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Original file line number Diff line number Diff line change
Expand Up @@ -115,6 +115,8 @@ static struct {
jmp_buf* (*png_set_longjmp_fn) (png_structrp, png_longjmp_ptr, size_t);
#endif
#endif
int (*png_image_begin_read_from_memory) (png_imagep image, png_const_voidp memory, size_t size);
int (*png_image_finish_read) (png_imagep image, png_const_colorp background, void *buffer, png_int_32 row_stride, void *colormap);
#if SDL_IMAGE_SAVE_PNG
png_structp (*png_create_write_struct) (png_const_charp user_png_ver, png_voidp error_ptr, png_error_ptr error_fn, png_error_ptr warn_fn);
void (*png_destroy_write_struct) (png_structpp png_ptr_ptr, png_infopp info_ptr_ptr);
Expand Down Expand Up @@ -170,6 +172,8 @@ int IMG_InitPNG()
FUNCTION_LOADER(png_set_longjmp_fn, jmp_buf* (*) (png_structrp, png_longjmp_ptr, size_t))
#endif
#endif
FUNCTION_LOADER(png_image_begin_read_from_memory, int (*) (png_imagep image, png_const_voidp memory, size_t size))
FUNCTION_LOADER(png_image_finish_read, int (*) (png_imagep image, png_const_colorp background, void *buffer, png_int_32 row_stride, void *colormap))
#if SDL_IMAGE_SAVE_PNG
FUNCTION_LOADER(png_create_write_struct, png_structp (*) (png_const_charp user_png_ver, png_voidp error_ptr, png_error_ptr error_fn, png_error_ptr warn_fn))
FUNCTION_LOADER(png_destroy_write_struct, void (*) (png_structpp png_ptr_ptr, png_infopp info_ptr_ptr))
Expand Down Expand Up @@ -224,6 +228,118 @@ int IMG_isPNG(SDL_RWops *src)
return(is_PNG);
}

SDL_Surface *IMG_LoadPNG_RW(SDL_RWops *src) {
png_image image;
Sint64 src_length;
Uint8* raw_image_buffer;
SDL_Surface *surface;
SDL_Palette* palette = NULL;
void* colormap = NULL;
Uint32 pixelformat;

if ( (IMG_Init(IMG_INIT_PNG) & IMG_INIT_PNG) == 0 ) {
return NULL;
}

/* This function uses libpng's "Simplified API" to read a PNG.
* See https://github.com/pnggroup/libpng/blob/libpng16/libpng-manual.txt
* And https://github.com/pnggroup/libpng/blob/libpng16/contrib/examples/pngtopng.c
* For information about this and example usage, respectively. */

/* Only the image structure version number needs to be set. */
SDL_memset(&image, 0, sizeof(image));
image.version = PNG_IMAGE_VERSION;

src_length = SDL_RWsize(src); //todo error check

printf("src_length=%i\n", src_length);

raw_image_buffer = SDL_malloc(src_length); // ec
SDL_RWseek(src, RW_SEEK_SET, 0); // ec
int objects_read = SDL_RWread(src, raw_image_buffer, 1, src_length); // ec

printf("objects_read=%i\n", objects_read);

if (lib.png_image_begin_read_from_memory(&image, raw_image_buffer, src_length)) {
/* If the image is natively encoded with a colormap, set the format to
/* PNG_FORMAT_RGBA_COLORMAP. This allows libpng to directly map into the
/* colors of an allocated SDL_Palette. Libpng handles mapping the native
/* colormap format into this consistent format. */

if (image.format & PNG_FORMAT_FLAG_COLORMAP) {
image.format = PNG_FORMAT_RGBA_COLORMAP;
pixelformat = SDL_PIXELFORMAT_INDEX8;

palette = SDL_AllocPalette(image.colormap_entries);
colormap = palette->colors;
SDL_assert(PNG_IMAGE_COLORMAP_SIZE(image) == palette->ncolors * 4);
}

/* Otherwise, maps the existing PNG format to a SDL pixelformatenum.
/* If no mapping is found it falls down to a default, libpng handles
/* conversion. */
else {
switch (image.format) {
case PNG_FORMAT_RGBA:
pixelformat = SDL_PIXELFORMAT_RGBA32;
break;
case PNG_FORMAT_ARGB:
pixelformat = SDL_PIXELFORMAT_ARGB32;
break;

/* Lets have grey alpha -> BGRA */
case PNG_FORMAT_GA:
image.format = PNG_FORMAT_BGRA;
case PNG_FORMAT_BGRA:
pixelformat = SDL_PIXELFORMAT_BGRA32;
break;

case PNG_FORMAT_ABGR:
pixelformat = SDL_PIXELFORMAT_ABGR32;
break;

/* Lets have gray (no alpha) -> RGB */
case PNG_FORMAT_GRAY:
image.format = PNG_FORMAT_RGB;
case PNG_FORMAT_RGB:
#if SDL_BYTEORDER == SDL_BIG_ENDIAN
pixelformat = SDL_PIXELFORMAT_BGR24;
#else
pixelformat = SDL_PIXELFORMAT_RGB24;
#endif
break;
case PNG_FORMAT_BGR:
#if SDL_BYTEORDER == SDL_BIG_ENDIAN
pixelformat = SDL_PIXELFORMAT_RGB24;
#else
pixelformat = SDL_PIXELFORMAT_BGR24;
#endif
break;

/* If it's another format, lets use BGRA by default */
default:
image.format = PNG_FORMAT_BGRA;
pixelformat = SDL_PIXELFORMAT_BGRA32;
}
}

surface = SDL_CreateRGBSurfaceWithFormat(0, image.width, image.height, 0, pixelformat);

if (palette != NULL) {
SDL_SetSurfacePalette(surface, palette);
}

lib.png_image_finish_read(&image, NULL, surface->pixels, surface->pitch, colormap);

return surface;
}

printf("image.message=%s\n", image.message);

SDL_SetError("FAILED");
return NULL;
}

/* Load a PNG type image from an SDL datasource */
static void png_read_data(png_structp ctx, png_bytep area, png_size_t size)
{
Expand All @@ -232,7 +348,7 @@ static void png_read_data(png_structp ctx, png_bytep area, png_size_t size)
src = (SDL_RWops *)lib.png_get_io_ptr(ctx);
SDL_RWread(src, area, size, 1);
}
SDL_Surface *IMG_LoadPNG_RW(SDL_RWops *src)
SDL_Surface *IMG_LoadPNG_RW2(SDL_RWops *src)
{
Sint64 start;
const char *error;
Expand Down Expand Up @@ -315,9 +431,13 @@ SDL_Surface *IMG_LoadPNG_RW(SDL_RWops *src)
*/
lib.png_set_packing(png_ptr);

printf("COLOR TYPE = %i\n", color_type);

/* scale greyscale values to the range 0..255 */
if (color_type == PNG_COLOR_TYPE_GRAY)
if (color_type == PNG_COLOR_TYPE_GRAY) {
printf("COLOR TYPE GRAY\n");
lib.png_set_expand(png_ptr);
}

/* For images with a single "transparent colour", set colour key;
if more than one index has transparency, or if partially transparent
Expand All @@ -327,7 +447,9 @@ SDL_Surface *IMG_LoadPNG_RW(SDL_RWops *src)
int num_trans;
Uint8 *trans;
lib.png_get_tRNS(png_ptr, info_ptr, &trans, &num_trans, &transv);
printf("here in the club\n");
if (color_type == PNG_COLOR_TYPE_PALETTE) {
printf("wowowowo\n");
/* Check if all tRNS entries are opaque except one */
int j, t = -1;
for (j = 0; j < num_trans; j++) {
Expand All @@ -352,6 +474,8 @@ SDL_Surface *IMG_LoadPNG_RW(SDL_RWops *src)
}
}

printf("done with that stuff\n");

if ( color_type == PNG_COLOR_TYPE_GRAY_ALPHA )
lib.png_set_gray_to_rgb(png_ptr);

Expand All @@ -363,6 +487,8 @@ SDL_Surface *IMG_LoadPNG_RW(SDL_RWops *src)
/* Allocate the SDL surface to hold the image */
num_channels = lib.png_get_channels(png_ptr, info_ptr);

printf("bit_depth = %i, num_channels = %i\n", bit_depth, num_channels);

format = SDL_PIXELFORMAT_UNKNOWN;
if (num_channels == 3) {
format = SDL_PIXELFORMAT_RGB24;
Expand Down Expand Up @@ -402,6 +528,13 @@ SDL_Surface *IMG_LoadPNG_RW(SDL_RWops *src)
}

if (ckey != -1) {
if (color_type == PNG_COLOR_TYPE_GRAY) {
/* FIXME: Should these be truncated or shifted down? */
ckey = SDL_MapRGB(surface->format,
(Uint8)transv->gray,
(Uint8)transv->gray,
(Uint8)transv->gray);
}
if (color_type != PNG_COLOR_TYPE_PALETTE) {
/* FIXME: Should these be truncated or shifted down? */
ckey = SDL_MapRGB(surface->format,
Expand Down

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