Como salvar una superficie SDL a un PNG y obtener los colores correctos?
https://stackoverflow.com/questions/718933
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escribí un simple parche para añadir capacidades al SDL_Image biblioteca PNG de ahorro . Casi funciona, también. El problema es que los colores salen todos los codificados, y yo no sé lo suficiente C para averiguar lo que está mal. ¿Alguien puede echar un vistazo a esto y ayudar a corregir el problema arriba?
Caso de uso:
- Carga una imagen de 256 colores PNG con
IMG_LoadPNG_RW. - Guárdelo con
IMG_SavePNG_RW. - A ver si son idénticos o no.
Patch:
Index: IMG_png.c
===================================================================
--- IMG_png.c (revision 4475)
+++ IMG_png.c (working copy)
@@ -76,17 +76,25 @@
png_infop (*png_create_info_struct) (png_structp png_ptr);
png_structp (*png_create_read_struct) (png_const_charp user_png_ver, png_voidp error_ptr, png_error_ptr error_fn, png_error_ptr warn_fn);
void (*png_destroy_read_struct) (png_structpp png_ptr_ptr, png_infopp info_ptr_ptr, png_infopp end_info_ptr_ptr);
+ 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);
png_uint_32 (*png_get_IHDR) (png_structp png_ptr, png_infop info_ptr, png_uint_32 *width, png_uint_32 *height, int *bit_depth, int *color_type, int *interlace_method, int *compression_method, int *filter_method);
+ void (*png_set_IHDR) (png_structp png_ptr, png_infop info_ptr, png_uint_32 width, png_uint_32 height, int bit_depth, int color_type, int interlace_method, int compression_method, int filter_method);
png_voidp (*png_get_io_ptr) (png_structp png_ptr);
png_uint_32 (*png_get_tRNS) (png_structp png_ptr, png_infop info_ptr, png_bytep *trans, int *num_trans, png_color_16p *trans_values);
png_uint_32 (*png_get_valid) (png_structp png_ptr, png_infop info_ptr, png_uint_32 flag);
void (*png_read_image) (png_structp png_ptr, png_bytepp image);
+ void (*png_write_image) (png_structp png_ptr, png_bytepp image);
void (*png_read_info) (png_structp png_ptr, png_infop info_ptr);
+ void (*png_write_info) (png_structp png_ptr, png_infop info_ptr);
+ void (*png_set_PLTE) (png_structp png_ptr, png_infop info_ptr, png_colorp palette, int num_palette);
+ void (*png_write_end) (png_structp png_ptr, png_infop info_ptr);
void (*png_read_update_info) (png_structp png_ptr, png_infop info_ptr);
void (*png_set_expand) (png_structp png_ptr);
void (*png_set_gray_to_rgb) (png_structp png_ptr);
void (*png_set_packing) (png_structp png_ptr);
void (*png_set_read_fn) (png_structp png_ptr, png_voidp io_ptr, png_rw_ptr read_data_fn);
+ void (*png_set_write_fn) (png_structp png_ptr, png_voidp io_ptr, png_rw_ptr read_data_fn);
void (*png_set_strip_16) (png_structp png_ptr);
int (*png_sig_cmp) (png_bytep sig, png_size_t start, png_size_t num_to_check);
} lib;
@@ -120,6 +128,20 @@
SDL_UnloadObject(lib.handle);
return -1;
}
+ lib.png_create_write_struct =
+ (png_structp (*) (png_const_charp, png_voidp, png_error_ptr, png_error_ptr))
+ SDL_LoadFunction(lib.handle, "png_create_write_struct");
+ if ( lib.png_create_write_struct == NULL ) {
+ SDL_UnloadObject(lib.handle);
+ return -1;
+ }
+ lib.png_destroy_write_struct =
+ (void (*) (png_structpp, png_infopp))
+ SDL_LoadFunction(lib.handle, "png_destroy_write_struct");
+ if ( lib.png_destroy_write_struct == NULL ) {
+ SDL_UnloadObject(lib.handle);
+ return -1;
+ }
lib.png_get_IHDR =
(png_uint_32 (*) (png_structp, png_infop, png_uint_32 *, png_uint_32 *, int *, int *, int *, int *, int *))
SDL_LoadFunction(lib.handle, "png_get_IHDR");
@@ -127,6 +149,13 @@
SDL_UnloadObject(lib.handle);
return -1;
}
+ lib.png_set_IHDR =
+ (void (*) (png_structp, png_infop, png_uint_32, png_uint_32, int, int, int, int, int))
+ SDL_LoadFunction(lib.handle, "png_set_IHDR");
+ if ( lib.png_set_IHDR == NULL ) {
+ SDL_UnloadObject(lib.handle);
+ return -1;
+ }
lib.png_get_io_ptr =
(png_voidp (*) (png_structp))
SDL_LoadFunction(lib.handle, "png_get_io_ptr");
@@ -155,6 +184,13 @@
SDL_UnloadObject(lib.handle);
return -1;
}
+ lib.png_write_image =
+ (void (*) (png_structp, png_bytepp))
+ SDL_LoadFunction(lib.handle, "png_write_image");
+ if ( lib.png_write_image == NULL ) {
+ SDL_UnloadObject(lib.handle);
+ return -1;
+ }
lib.png_read_info =
(void (*) (png_structp, png_infop))
SDL_LoadFunction(lib.handle, "png_read_info");
@@ -162,6 +198,27 @@
SDL_UnloadObject(lib.handle);
return -1;
}
+ lib.png_write_info =
+ (void (*) (png_structp, png_infop))
+ SDL_LoadFunction(lib.handle, "png_write_info");
+ if ( lib.png_write_info == NULL ) {
+ SDL_UnloadObject(lib.handle);
+ return -1;
+ }
+ lib.png_set_PLTE =
+ (void (*) (png_structp, png_infop, png_colorp, int))
+ SDL_LoadFunction(lib.handle, "png_set_PLTE");
+ if ( lib.png_set_PLTE == NULL ) {
+ SDL_UnloadObject(lib.handle);
+ return -1;
+ }
+ lib.png_write_end =
+ (void (*) (png_structp, png_infop))
+ SDL_LoadFunction(lib.handle, "png_write_end");
+ if ( lib.png_write_end == NULL ) {
+ SDL_UnloadObject(lib.handle);
+ return -1;
+ }
lib.png_read_update_info =
(void (*) (png_structp, png_infop))
SDL_LoadFunction(lib.handle, "png_read_update_info");
@@ -197,6 +254,13 @@
SDL_UnloadObject(lib.handle);
return -1;
}
+ lib.png_set_write_fn =
+ (void (*) (png_structp, png_voidp, png_rw_ptr))
+ SDL_LoadFunction(lib.handle, "png_set_write_fn");
+ if ( lib.png_set_write_fn == NULL ) {
+ SDL_UnloadObject(lib.handle);
+ return -1;
+ }
lib.png_set_strip_16 =
(void (*) (png_structp))
SDL_LoadFunction(lib.handle, "png_set_strip_16");
@@ -472,7 +536,7 @@
palette->colors[i].g = i;
palette->colors[i].b = i;
}
- } else if (info_ptr->num_palette > 0 ) {
+ } else if (info_ptr->num_palette > 0 ) {
palette->ncolors = info_ptr->num_palette;
for( i=0; i<info_ptr->num_palette; ++i ) {
palette->colors[i].b = info_ptr->palette[i].blue;
@@ -505,18 +569,167 @@
return(surface);
}
-#else
+static void png_write_data(png_structp ctx, png_bytep area, png_size_t size)
+{
+ SDL_RWops *src;
-/* See if an image is contained in a data source */
-int IMG_isPNG(SDL_RWops *src)
+ src = (SDL_RWops *)lib.png_get_io_ptr(ctx);
+ SDL_RWwrite(src, area, size, 1);
+}
+/* write a png file */
+int IMG_SavePNG_RW(SDL_Surface *surface, SDL_RWops *src)
{
- return(0);
-}
+ png_structp png_ptr;
+ png_infop info_ptr;
+ png_colorp palette = NULL;
+ int start;
+ int colorType;
+ int i;
+ const char *error;
+ SDL_Palette *sdlPalette;
+ png_uint_32 height = surface->h;
+ png_uint_32 width = surface->w;
+ png_bytep *volatile row_pointers;
+ int row;
-/* Load a PNG type image from an SDL datasource */
-SDL_Surface *IMG_LoadPNG_RW(SDL_RWops *src)
-{
- return(NULL);
+ if ( !src ) {
+ /* The error message has been set in SDL_RWFromFile */
+ return -1;
+ }
+ start = SDL_RWtell(src);
+
+ if ( IMG_InitPNG() < 0 ) {
+ return -1;
+ }
+
+ /* 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 check that
+ * the library version is compatible with the one used at compile time,
+ * in case we are using dynamically linked libraries. REQUIRED.
+ */
+ png_ptr = NULL; info_ptr = NULL;
+
+ /* Create the PNG loading context structure */
+ png_ptr = lib.png_create_read_struct(PNG_LIBPNG_VER_STRING,
+ NULL,NULL,NULL);
+ if (png_ptr == NULL){
+ error = "Couldn't allocate memory for PNG file or incompatible PNG dll";
+ goto done;
+ }
+
+ /* Allocate/initialize the memory for image information. REQUIRED. */
+ info_ptr = lib.png_create_info_struct(png_ptr);
+ if (info_ptr == NULL) {
+ error = "Couldn't create image information for PNG file";
+ goto done;
+ }
+
+ /* Set error handling if you are using setjmp/longjmp method (this is
+ * the normal method of doing things with libpng). REQUIRED unless you
+ * set up your own error handlers in png_create_read_struct() earlier.
+ */
+ if ( setjmp(png_ptr->jmpbuf) ) {
+ error = "Error reading the PNG file.";
+ goto done;
+ }
+
+ /* Set up the output control */
+ lib.png_set_write_fn(png_ptr, src, png_write_data);
+
+ /* Set the image information here. Width and height are up to 2^31,
+ * bit_depth is one of 1, 2, 4, 8, or 16, but valid values also depend on
+ * the color_type selected. color_type is one of PNG_COLOR_TYPE_GRAY,
+ * PNG_COLOR_TYPE_GRAY_ALPHA, PNG_COLOR_TYPE_PALETTE, PNG_COLOR_TYPE_RGB,
+ * or PNG_COLOR_TYPE_RGB_ALPHA. interlace is either PNG_INTERLACE_NONE or
+ * PNG_INTERLACE_ADAM7, and the compression_type and filter_type MUST
+ * currently be PNG_COMPRESSION_TYPE_BASE and PNG_FILTER_TYPE_BASE. REQUIRED
+ */
+ sdlPalette = surface->format->palette;
+ if (sdlPalette)
+ {
+ colorType = PNG_COLOR_TYPE_PALETTE;
+ } else if (surface->format->Amask)
+ {
+ colorType = PNG_COLOR_TYPE_RGB_ALPHA;
+ } else
+ {
+ colorType = PNG_COLOR_TYPE_RGB;
+ }
+ lib.png_set_IHDR(png_ptr, info_ptr, surface->w, surface->h, surface->format->BitsPerPixel, colorType,
+ PNG_INTERLACE_NONE, PNG_COMPRESSION_TYPE_BASE, PNG_FILTER_TYPE_BASE);
+
+ /* set the palette if there is one. REQUIRED for indexed-color images */
+ if (colorType == PNG_COLOR_TYPE_PALETTE)
+ {
+ palette = (png_colorp) malloc(sdlPalette->ncolors * sizeof(png_color));
+
+ for( i=0; i < sdlPalette->ncolors; ++i ) {
+ palette[i].blue = sdlPalette->colors[i].b;
+ palette[i].green = sdlPalette->colors[i].g;
+ palette[i].red = sdlPalette->colors[i].r;
+ }
+ lib.png_set_PLTE(png_ptr, info_ptr, palette, sdlPalette->ncolors);
+ }
+ else
+ { //not sure how to handle this
+// sig_bit.red = true_red_bit_depth;
+// sig_bit.green = true_green_bit_depth;
+// sig_bit.blue = true_blue_bit_depth;
+ /* if the image has an alpha channel then */
+// sig_bit.alpha = true_alpha_bit_depth;
+// png_set_sBIT(png_ptr, info_ptr, sig_bit);
+ }
+
+ /* Write the file header information. REQUIRED */
+ lib.png_write_info(png_ptr, info_ptr);
+
+ /* The easiest way to write the image (you may have a different memory
+ * layout, however, so choose what fits your needs best). You need to
+ * use the first method if you aren't handling interlacing yourself.
+ */
+
+ row_pointers = (png_bytep*) malloc(sizeof(png_bytep)*height);
+ if ( (row_pointers == NULL) ) {
+ error = "Out of memory";
+ goto done;
+ }
+ for (row = 0; row < (int)height; row++) {
+ row_pointers[row] = (png_bytep)
+ (Uint8 *)surface->pixels + row*surface->pitch;
+ }
+
+ if (height > PNG_UINT_32_MAX/sizeof(png_bytep))
+ {
+ error = "Image is too tall to process in memory";
+ goto done;
+ }
+
+ /* Read the entire image in one go */
+ lib.png_write_image(png_ptr, row_pointers);
+
+ /* It is REQUIRED to call this to finish writing the rest of the file */
+ lib.png_write_end(png_ptr, info_ptr);
+
+done: /* Clean up and return */
+ if ( png_ptr ) {
+ lib.png_destroy_write_struct(&png_ptr, &info_ptr);
+ }
+ if ( row_pointers ) {
+ free(row_pointers);
+ }
+ if (palette)
+ {
+ free(palette);
+ }
+ if ( error ) {
+ IMG_QuitPNG();
+ IMG_SetError(error);
+ return(-1);
+ } else {
+ IMG_QuitPNG();
+ }
+ return(0);
}
#endif /* LOAD_PNG */
Index: SDL_image.h
===================================================================
--- SDL_image.h (revision 4475)
+++ SDL_image.h (working copy)
@@ -107,6 +107,8 @@
extern DECLSPEC SDL_Surface * SDLCALL IMG_ReadXPMFromArray(char **xpm);
+extern DECLSPEC int SDLCALL IMG_SavePNG_RW(SDL_Surface *surface, SDL_RWops *src);
+
/* We'll use SDL for reporting errors */
#define IMG_SetError SDL_SetError
#define IMG_GetError SDL_GetError
Solución 2
Me las arreglé para conseguir que funcione. Necesitaba llamar png_set_bgr () para fijar la paleta.
Otros consejos
Ahorro de superficies SDL como imágenes PNG es un problema que se ha resuelto en la web varias veces:
http://www.bishoujo.us/svn/renpy/trunk/module/
http://lists.libsdl.org/pipermail/ sdl-libsdl.org/2006-May/055936.html
http://www.os4depot.net/index. php? = funcionar showfile y desarrollo file = / ejemplo / sdlpngsavesurf.lha
http://encelo.netsons.org/programming/sdl
En lugar de pedir ayuda depurar una cantidad significativa de código, comparando el código para esas otras implementaciones y ver dónde está la diferencia, o preguntando cuál de esas otras implementaciones es la mejor manera de utilizar, probablemente sería más productivo.
Como acotación al margen, la biblioteca de parches SDL_image podría ser una solución menos robusta que la escritura bibliotecas dependientes separadas para poner en práctica el ahorro de PNG. De esa manera la próxima actualización SDL no romper su código. Si estabas pensando en que contribuye el parche a SDL, todas las otras implementaciones mencionadas se remontan unos años. No creo que SDL_image no incluye PNG ahorrar para la falta de cualquiera que desee o ser capaz de codificar la misma.
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