建档

Library/SDL2_image-2.5.2/IMG_stb.c

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+/*
+  SDL_image:  An example image loading library for use with SDL
+  Copyright (C) 1997-2018 Sam Lantinga <slouken@libsdl.org>
+
+  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.
+*/
+
+#include "SDL_image.h"
+
+#ifdef USE_STBIMAGE
+
+#ifndef INT_MAX
+#define INT_MAX 0x7FFFFFFF
+#endif
+
+#define malloc SDL_malloc
+#define realloc SDL_realloc
+#define free SDL_free
+#undef memcpy
+#define memcpy SDL_memcpy
+#undef memset
+#define memset SDL_memset
+#undef strcmp
+#define strcmp SDL_strcmp
+#undef strncmp
+#define strncmp SDL_strncmp
+#define strtol SDL_strtol
+
+#define pow SDL_pow
+#define ldexp SDL_scalbn
+
+#define STB_IMAGE_STATIC
+#define STBI_NO_THREAD_LOCALS
+#define STBI_FAILURE_USERMSG
+#if defined(__ARM_NEON)
+#define STBI_NEON
+#endif
+#define STBI_NO_STDIO
+#define STBI_ONLY_PNG
+#define STBI_ONLY_JPEG
+#define STBI_NO_GIF
+#define STBI_NO_HDR
+#define STBI_NO_LINEAR
+#define STBI_ASSERT SDL_assert
+#define STB_IMAGE_IMPLEMENTATION
+#include "stb_image.h"
+
+static int IMG_LoadSTB_RW_read(void *user, char *data, int size)
+{
+    return (int) SDL_RWread((SDL_RWops*) user, data, 1, size);
+}
+
+static void IMG_LoadSTB_RW_skip(void *user, int n)
+{
+    SDL_RWseek((SDL_RWops*) user, n, RW_SEEK_CUR);
+}
+
+static int IMG_LoadSTB_RW_eof(void *user)
+{
+    /* FIXME: Do we not have a way to detect EOF? -flibit */
+    size_t bytes, filler;
+    SDL_RWops *src = (SDL_RWops*) user;
+    bytes = SDL_RWread(src, &filler, 1, 1);
+    if (bytes != 1) { /* FIXME: Could also be an error... */
+        return 1;
+    }
+    SDL_RWseek(src, -1, RW_SEEK_CUR);
+    return 0;
+}
+
+SDL_Surface *IMG_LoadSTB_RW(SDL_RWops *src)
+{
+    Sint64 start;
+    int w, h, format;
+#if SDL_BYTEORDER == SDL_BIG_ENDIAN
+    int shift;
+#endif
+    Uint32 rmask, gmask, bmask, amask;
+    stbi_uc *pixels;
+    stbi_io_callbacks rw_callbacks;
+    SDL_Surface *surface = NULL;
+
+    if ( !src ) {
+        /* The error message has been set in SDL_RWFromFile */
+        return NULL;
+    }
+    start = SDL_RWtell(src);
+
+    /* Load the image data */
+    rw_callbacks.read = IMG_LoadSTB_RW_read;
+    rw_callbacks.skip = IMG_LoadSTB_RW_skip;
+    rw_callbacks.eof = IMG_LoadSTB_RW_eof;
+    pixels = stbi_load_from_callbacks(
+        &rw_callbacks,
+        src,
+        &w,
+        &h,
+        &format,
+        STBI_default
+    );
+    if ( !pixels ) {
+        SDL_RWseek(src, start, RW_SEEK_SET);
+        return NULL;
+    }
+
+    /* Determine the surface format */
+    SDL_assert(format == STBI_rgb || format == STBI_rgb_alpha);
+#if SDL_BYTEORDER == SDL_BIG_ENDIAN
+    shift = (format == STBI_rgb) ? 8 : 0;
+    rmask = 0xFF000000 >> shift;
+    gmask = 0x00FF0000 >> shift;
+    bmask = 0x0000FF00 >> shift;
+    amask = 0x000000FF >> shift;
+#else /* little endian, like x86 */
+    rmask = 0x000000FF;
+    gmask = 0x0000FF00;
+    bmask = 0x00FF0000;
+    amask = (format == STBI_rgb) ? 0 : 0xFF000000;
+#endif
+
+    /* Allocate the surface */
+    surface = SDL_CreateRGBSurfaceFrom(
+        pixels,
+        w,
+        h,
+        8 * format,
+        w * format,
+        rmask,
+        gmask,
+        bmask,
+        amask
+    );
+    if ( !surface ) {
+        /* The error message should already be set */
+        stbi_image_free(pixels); /* calls SDL_free() */
+        SDL_RWseek(src, start, RW_SEEK_SET);
+    } else {
+        /* FIXME: This sucks. It'd be better to allocate the surface first, then
+         * write directly to the pixel buffer:
+         * https://github.com/nothings/stb/issues/58
+         * -flibit
+         */
+        surface->flags &= ~SDL_PREALLOC;
+    }
+    return surface;
+}
+
+#endif /* USE_STBIMAGE */