IMG_tga.c
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SDL_image: An example image loading library for use with SDL
Copyright (C) 1999, 2000, 2001 Sam Lantinga
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This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public
License as published by the Free Software Foundation; either
version 2 of the License, or (at your option) any later version.
This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Library General Public License for more details.
You should have received a copy of the GNU Library General Public
License along with this library; if not, write to the Free
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
Sam Lantinga
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slouken@libsdl.org
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*/
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/* $Id$ */
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#include <stdlib.h>
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#include <stdio.h>
#include <string.h>
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#include "SDL_endian.h"
#include "SDL_image.h"
#ifdef LOAD_TGA
/*
* A TGA loader for the SDL library
* Supports: Reading 8, 15, 16, 24 and 32bpp images, with alpha or colourkey,
* uncompressed or RLE encoded.
*
* 2000-06-10 Mattias Engdegård <f91-men@nada.kth.se>: initial version
* 2000-06-26 Mattias Engdegård <f91-men@nada.kth.se>: read greyscale TGAs
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* 2000-08-09 Mattias Engdegård <f91-men@nada.kth.se>: alpha inversion removed
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*/
struct TGAheader {
Uint8 infolen; /* length of info field */
Uint8 has_cmap; /* 1 if image has colormap, 0 otherwise */
Uint8 type;
Uint8 cmap_start[2]; /* index of first colormap entry */
Uint8 cmap_len[2]; /* number of entries in colormap */
Uint8 cmap_bits; /* bits per colormap entry */
Uint8 yorigin[2]; /* image origin (ignored here) */
Uint8 xorigin[2];
Uint8 width[2]; /* image size */
Uint8 height[2];
Uint8 pixel_bits; /* bits/pixel */
Uint8 flags;
};
enum tga_type {
TGA_TYPE_INDEXED = 1,
TGA_TYPE_RGB = 2,
TGA_TYPE_BW = 3,
TGA_TYPE_RLE_INDEXED = 9,
TGA_TYPE_RLE_RGB = 10,
TGA_TYPE_RLE_BW = 11
};
#define TGA_INTERLEAVE_MASK 0xc0
#define TGA_INTERLEAVE_NONE 0x00
#define TGA_INTERLEAVE_2WAY 0x40
#define TGA_INTERLEAVE_4WAY 0x80
#define TGA_ORIGIN_MASK 0x30
#define TGA_ORIGIN_LEFT 0x00
#define TGA_ORIGIN_RIGHT 0x10
#define TGA_ORIGIN_LOWER 0x00
#define TGA_ORIGIN_UPPER 0x20
/* read/write unaligned little-endian 16-bit ints */
#define LE16(p) ((p)[0] + ((p)[1] << 8))
#define SETLE16(p, v) ((p)[0] = (v), (p)[1] = (v) >> 8)
static void unsupported(void)
{
IMG_SetError("unsupported TGA format");
}
/* Load a TGA type image from an SDL datasource */
SDL_Surface *IMG_LoadTGA_RW(SDL_RWops *src)
{
struct TGAheader hdr;
int rle = 0;
int alpha = 0;
int indexed = 0;
int grey = 0;
int ckey = -1;
int ncols, w, h;
SDL_Surface *img;
Uint32 rmask, gmask, bmask, amask;
Uint8 *dst;
int i;
int bpp;
int lstep;
Uint32 pixel;
int count, rep;
if(!SDL_RWread(src, &hdr, sizeof(hdr), 1))
goto error;
ncols = LE16(hdr.cmap_len);
switch(hdr.type) {
case TGA_TYPE_RLE_INDEXED:
rle = 1;
/* fallthrough */
case TGA_TYPE_INDEXED:
if(!hdr.has_cmap || hdr.pixel_bits != 8 || ncols > 256)
goto error;
indexed = 1;
break;
case TGA_TYPE_RLE_RGB:
rle = 1;
/* fallthrough */
case TGA_TYPE_RGB:
indexed = 0;
break;
case TGA_TYPE_RLE_BW:
rle = 1;
/* fallthrough */
case TGA_TYPE_BW:
if(hdr.pixel_bits != 8)
goto error;
/* Treat greyscale as 8bpp indexed images */
indexed = grey = 1;
break;
default:
unsupported();
return NULL;
}
bpp = (hdr.pixel_bits + 7) >> 3;
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rmask = gmask = bmask = amask = 0;
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switch(hdr.pixel_bits) {
case 8:
if(!indexed) {
unsupported();
return NULL;
}
break;
case 15:
case 16:
/* 15 and 16bpp both seem to use 5 bits/plane. The extra alpha bit
is ignored for now. */
rmask = 0x7c00;
gmask = 0x03e0;
bmask = 0x001f;
break;
case 32:
alpha = 1;
/* fallthrough */
case 24:
if(SDL_BYTEORDER == SDL_BIG_ENDIAN) {
int s = alpha ? 0 : 8;
amask = 0x000000ff >> s;
rmask = 0x0000ff00 >> s;
gmask = 0x00ff0000 >> s;
bmask = 0xff000000 >> s;
} else {
amask = alpha ? 0xff000000 : 0;
rmask = 0x00ff0000;
gmask = 0x0000ff00;
bmask = 0x000000ff;
}
break;
default:
unsupported();
return NULL;
}
if((hdr.flags & TGA_INTERLEAVE_MASK) != TGA_INTERLEAVE_NONE
|| hdr.flags & TGA_ORIGIN_RIGHT) {
unsupported();
return NULL;
}
SDL_RWseek(src, hdr.infolen, SEEK_CUR); /* skip info field */
w = LE16(hdr.width);
h = LE16(hdr.height);
img = SDL_CreateRGBSurface(SDL_SWSURFACE, w, h,
bpp * 8,
rmask, gmask, bmask, amask);
if(hdr.has_cmap) {
int palsiz = ncols * ((hdr.cmap_bits + 7) >> 3);
if(indexed && !grey) {
Uint8 *pal = malloc(palsiz), *p = pal;
SDL_Color *colors = img->format->palette->colors;
img->format->palette->ncolors = ncols;
SDL_RWread(src, pal, palsiz, 1);
for(i = 0; i < ncols; i++) {
switch(hdr.cmap_bits) {
case 15:
case 16:
{
Uint16 c = p[0] + (p[1] << 8);
p += 2;
colors[i].r = (c >> 7) & 0xf8;
colors[i].g = (c >> 2) & 0xf8;
colors[i].b = c << 3;
}
break;
case 24:
case 32:
colors[i].b = *p++;
colors[i].g = *p++;
colors[i].r = *p++;
if(hdr.cmap_bits == 32 && *p++ < 128)
ckey = i;
break;
}
}
free(pal);
if(ckey >= 0)
SDL_SetColorKey(img, SDL_SRCCOLORKEY, ckey);
} else {
/* skip unneeded colormap */
SDL_RWseek(src, palsiz, SEEK_CUR);
}
}
if(grey) {
SDL_Color *colors = img->format->palette->colors;
for(i = 0; i < 256; i++)
colors[i].r = colors[i].g = colors[i].b = i;
img->format->palette->ncolors = 256;
}
if(hdr.flags & TGA_ORIGIN_UPPER) {
lstep = img->pitch;
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dst = img->pixels;
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} else {
lstep = -img->pitch;
dst = (Uint8 *)img->pixels + (h - 1) * img->pitch;
}
/* The RLE decoding code is slightly convoluted since we can't rely on
spans not to wrap across scan lines */
count = rep = 0;
for(i = 0; i < h; i++) {
if(rle) {
int x = 0;
for(;;) {
Uint8 c;
if(count) {
int n = count;
if(n > w - x)
n = w - x;
SDL_RWread(src, dst + x * bpp, n * bpp, 1);
count -= n;
x += n;
if(x == w)
break;
} else if(rep) {
int n = rep;
if(n > w - x)
n = w - x;
rep -= n;
while(n--) {
memcpy(dst + x * bpp, &pixel, bpp);
x++;
}
if(x == w)
break;
}
SDL_RWread(src, &c, 1, 1);
if(c & 0x80) {
SDL_RWread(src, &pixel, bpp, 1);
rep = (c & 0x7f) + 1;
} else {
count = c + 1;
}
}
} else {
SDL_RWread(src, dst, w * bpp, 1);
}
if(SDL_BYTEORDER == SDL_BIG_ENDIAN && bpp == 2) {
/* swap byte order */
int x;
Uint16 *p = (Uint16 *)dst;
for(x = 0; x < w; x++)
p[x] = SDL_Swap16(p[x]);
}
dst += lstep;
}
return img;
error:
IMG_SetError("Error reading TGA data");
return NULL;
}
#else
/* dummy TGA load routine */
SDL_Surface *IMG_LoadTGA_RW(SDL_RWops *src)
{
return(NULL);
}
#endif /* LOAD_TGA */