SDL_image: An example image loading library for use with SDL

Copyright (C) 1997-2012 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.

*/

#if !defined(__APPLE__) || defined(SDL_IMAGE_USE_COMMON_BACKEND)

/* This is a GIF image file loading framework */

#include <stdio.h>

#include <string.h>

#include "SDL_image.h"

#ifdef LOAD_GIF

/* See if an image is contained in a data source */

int IMG_isGIF(SDL_RWops *src)

{

int is_GIF;

char magic[6];

if ( !src )

return 0;

if ( (strncmp(magic, "GIF", 3) == 0) &&

((memcmp(magic + 3, "87a", 3) == 0) ||

(memcmp(magic + 3, "89a", 3) == 0)) ) {

is_GIF = 1;

}

}

return(is_GIF);

}

/* Code from here to end of file has been adapted from XPaint: */

/* +-------------------------------------------------------------------+ */

/* | Copyright 1990, 1991, 1993 David Koblas. | */

/* | Copyright 1996 Torsten Martinsen. | */

/* | Permission to use, copy, modify, and distribute this software | */

/* | and its documentation for any purpose and without fee is hereby | */

/* | granted, provided that the above copyright notice appear in all | */

/* | copies and that both that copyright notice and this permission | */

/* | notice appear in supporting documentation. This software is | */

/* | provided "as is" without express or implied warranty. | */

/* +-------------------------------------------------------------------+ */

/* Adapted for use in SDL by Sam Lantinga -- 7/20/98 */

#define USED_BY_SDL

#include <stdio.h>

#include <string.h>

#ifdef USED_BY_SDL

/* Changes to work with SDL:

Include SDL header file

Use SDL_Surface rather than xpaint Image structure

Define SDL versions of RWSetMsg(), ImageNewCmap() and ImageSetCmap()

*/

#include "SDL.h"

#define Image SDL_Surface

#define RWSetMsg IMG_SetError

#define ImageNewCmap(w, h, s) SDL_AllocSurface(SDL_SWSURFACE,w,h,8,0,0,0,0)

#define ImageSetCmap(s, i, R, G, B) do { \

s->format->palette->colors[i].r = R; \

s->format->palette->colors[i].g = G; \

s->format->palette->colors[i].b = B; \

} while (0)

/* * * * * */

#else

/* Original XPaint sources */

#include "image.h"

#include "rwTable.h"

#define SDL_RWops FILE

#define SDL_RWclose fclose

#endif /* USED_BY_SDL */

#define MAXCOLORMAPSIZE 256

#define TRUE 1

#define FALSE 0

#define CM_RED 0

#define CM_GREEN 1

#define CM_BLUE 2

#define MAX_LWZ_BITS 12

#define INTERLACE 0x40

#define LOCALCOLORMAP 0x80

#define BitSet(byte, bit) (((byte) & (bit)) == (bit))

#define ReadOK(file,buffer,len) SDL_RWread(file, buffer, len, 1)

#define LM_to_uint(a,b) (((b)<<8)|(a))

unsigned int Width;

unsigned int Height;

unsigned char ColorMap[3][MAXCOLORMAPSIZE];

unsigned int BitPixel;

unsigned int ColorResolution;

unsigned int Background;

unsigned int AspectRatio;

int GrayScale;

} GifScreen;

static struct {

int transparent;

int delayTime;

int inputFlag;

int disposal;

} Gif89;

static int ReadColorMap(SDL_RWops * src, int number,

unsigned char buffer[3][MAXCOLORMAPSIZE], int *flag);

static int DoExtension(SDL_RWops * src, int label);

static int GetDataBlock(SDL_RWops * src, unsigned char *buf);

static int GetCode(SDL_RWops * src, int code_size, int flag);

static int LWZReadByte(SDL_RWops * src, int flag, int input_code_size);

static Image *ReadImage(SDL_RWops * src, int len, int height, int,

unsigned char cmap[3][MAXCOLORMAPSIZE],

int gray, int interlace, int ignore);

Image *

IMG_LoadGIF_RW(SDL_RWops *src)

{

unsigned char buf[16];

unsigned char c;

unsigned char localColorMap[3][MAXCOLORMAPSIZE];

int grayScale;

int useGlobalColormap;

int bitPixel;

int imageCount = 0;

char version[4];

int imageNumber = 1;

Image *image = NULL;

if ( src == NULL ) {

start = SDL_RWtell(src);

if (!ReadOK(src, buf, 6)) {

RWSetMsg("error reading magic number");

goto done;

}

if (strncmp((char *) buf, "GIF", 3) != 0) {

RWSetMsg("not a GIF file");

goto done;

}

version[3] = '\0';

if ((strcmp(version, "87a") != 0) && (strcmp(version, "89a") != 0)) {

RWSetMsg("bad version number, not '87a' or '89a'");

goto done;

}

Gif89.transparent = -1;

Gif89.delayTime = -1;

Gif89.inputFlag = -1;

Gif89.disposal = 0;

if (!ReadOK(src, buf, 7)) {

RWSetMsg("failed to read screen descriptor");

goto done;

}

GifScreen.Width = LM_to_uint(buf[0], buf[1]);

GifScreen.Height = LM_to_uint(buf[2], buf[3]);

GifScreen.BitPixel = 2 << (buf[4] & 0x07);

GifScreen.ColorResolution = (((buf[4] & 0x70) >> 3) + 1);

GifScreen.Background = buf[5];

GifScreen.AspectRatio = buf[6];

if (BitSet(buf[4], LOCALCOLORMAP)) { /* Global Colormap */

if (ReadColorMap(src, GifScreen.BitPixel, GifScreen.ColorMap,

&GifScreen.GrayScale)) {

RWSetMsg("error reading global colormap");

goto done;

}

}

do {

if (!ReadOK(src, &c, 1)) {

RWSetMsg("EOF / read error on image data");

goto done;

}

if (c == ';') { /* GIF terminator */

if (imageCount < imageNumber) {

RWSetMsg("only %d image%s found in file",

imageCount, imageCount > 1 ? "s" : "");

goto done;

}

}

if (c == '!') { /* Extension */

if (!ReadOK(src, &c, 1)) {

RWSetMsg("EOF / read error on extention function code");

goto done;

}

DoExtension(src, c);

continue;

}

if (c != ',') { /* Not a valid start character */

continue;

}

++imageCount;

if (!ReadOK(src, buf, 9)) {

RWSetMsg("couldn't read left/top/width/height");

goto done;

}

useGlobalColormap = !BitSet(buf[8], LOCALCOLORMAP);

bitPixel = 1 << ((buf[8] & 0x07) + 1);

if (!useGlobalColormap) {

if (ReadColorMap(src, bitPixel, localColorMap, &grayScale)) {

RWSetMsg("error reading local colormap");

goto done;

}

image = ReadImage(src, LM_to_uint(buf[4], buf[5]),

LM_to_uint(buf[6], buf[7]),

bitPixel, localColorMap, grayScale,

BitSet(buf[8], INTERLACE),

imageCount != imageNumber);

} else {

image = ReadImage(src, LM_to_uint(buf[4], buf[5]),

LM_to_uint(buf[6], buf[7]),

GifScreen.BitPixel, GifScreen.ColorMap,

GifScreen.GrayScale, BitSet(buf[8], INTERLACE),

imageCount != imageNumber);

}

} while (image == NULL);

#ifdef USED_BY_SDL

}

#endif

done:

return image;

}

static int

ReadColorMap(SDL_RWops *src, int number,

unsigned char buffer[3][MAXCOLORMAPSIZE], int *gray)

{

int i;

unsigned char rgb[3];

int flag;

flag = TRUE;

for (i = 0; i < number; ++i) {

if (!ReadOK(src, rgb, sizeof(rgb))) {

RWSetMsg("bad colormap");

return 1;

}

buffer[CM_RED][i] = rgb[0];

buffer[CM_GREEN][i] = rgb[1];

buffer[CM_BLUE][i] = rgb[2];

flag &= (rgb[0] == rgb[1] && rgb[1] == rgb[2]);

}

#if 0

if (flag)

*gray = (number == 2) ? PBM_TYPE : PGM_TYPE;

else

*gray = PPM_TYPE;

#else

*gray = 0;

#endif

return FALSE;

}

static int

DoExtension(SDL_RWops *src, int label)

{

static unsigned char buf[256];

char *str;

switch (label) {

case 0x01: /* Plain Text Extension */

str = "Plain Text Extension";

break;

case 0xff: /* Application Extension */

str = "Application Extension";

break;

case 0xfe: /* Comment Extension */

str = "Comment Extension";

while (GetDataBlock(src, (unsigned char *) buf) != 0)

;

return FALSE;

case 0xf9: /* Graphic Control Extension */

str = "Graphic Control Extension";

(void) GetDataBlock(src, (unsigned char *) buf);

Gif89.disposal = (buf[0] >> 2) & 0x7;

Gif89.inputFlag = (buf[0] >> 1) & 0x1;

Gif89.delayTime = LM_to_uint(buf[1], buf[2]);

if ((buf[0] & 0x1) != 0)

Gif89.transparent = buf[3];

while (GetDataBlock(src, (unsigned char *) buf) != 0)

;

return FALSE;

default:

str = (char *)buf;

sprintf(str, "UNKNOWN (0x%02x)", label);

break;

}

while (GetDataBlock(src, (unsigned char *) buf) != 0)

;

return FALSE;

}

static int ZeroDataBlock = FALSE;

static int

GetDataBlock(SDL_RWops *src, unsigned char *buf)

{

unsigned char count;

if (!ReadOK(src, &count, 1)) {

/* pm_message("error in getting DataBlock size" ); */

return -1;

}

ZeroDataBlock = count == 0;

if ((count != 0) && (!ReadOK(src, buf, count))) {

/* pm_message("error in reading DataBlock" ); */

return -1;

}

return count;

}

static int

GetCode(SDL_RWops *src, int code_size, int flag)

{

static unsigned char buf[280];

static int curbit, lastbit, done, last_byte;

int i, j, ret;

unsigned char count;

if (flag) {

curbit = 0;

lastbit = 0;

done = FALSE;

return 0;

}

if ((curbit + code_size) >= lastbit) {

if (done) {

if (curbit >= lastbit)

RWSetMsg("ran off the end of my bits");

return -1;

}

buf[0] = buf[last_byte - 2];

buf[1] = buf[last_byte - 1];

if ((count = GetDataBlock(src, &buf[2])) == 0)

done = TRUE;

last_byte = 2 + count;

curbit = (curbit - lastbit) + 16;

lastbit = (2 + count) * 8;

}

ret = 0;

for (i = curbit, j = 0; j < code_size; ++i, ++j)

ret |= ((buf[i / 8] & (1 << (i % 8))) != 0) << j;

curbit += code_size;

return ret;

}

static int

LWZReadByte(SDL_RWops *src, int flag, int input_code_size)

{

static int fresh = FALSE;

int code, incode;

static int code_size, set_code_size;

static int max_code, max_code_size;

static int firstcode, oldcode;

static int clear_code, end_code;

static int table[2][(1 << MAX_LWZ_BITS)];

static int stack[(1 << (MAX_LWZ_BITS)) * 2], *sp;

register int i;

/* Fixed buffer overflow found by Michael Skladnikiewicz */

if (input_code_size > MAX_LWZ_BITS)

return -1;

if (flag) {

set_code_size = input_code_size;

code_size = set_code_size + 1;

clear_code = 1 << set_code_size;

end_code = clear_code + 1;

max_code_size = 2 * clear_code;

max_code = clear_code + 2;

GetCode(src, 0, TRUE);

fresh = TRUE;

for (i = 0; i < clear_code; ++i) {

table[0][i] = 0;

table[1][i] = i;

}

for (; i < (1 << MAX_LWZ_BITS); ++i)

table[0][i] = table[1][0] = 0;

sp = stack;

return 0;

} else if (fresh) {

fresh = FALSE;

do {

firstcode = oldcode = GetCode(src, code_size, FALSE);

} while (firstcode == clear_code);

return firstcode;

}

if (sp > stack)

return *--sp;

while ((code = GetCode(src, code_size, FALSE)) >= 0) {

if (code == clear_code) {

for (i = 0; i < clear_code; ++i) {

table[0][i] = 0;

table[1][i] = i;

}

for (; i < (1 << MAX_LWZ_BITS); ++i)

table[0][i] = table[1][i] = 0;

code_size = set_code_size + 1;

max_code_size = 2 * clear_code;

max_code = clear_code + 2;

sp = stack;

firstcode = oldcode = GetCode(src, code_size, FALSE);

return firstcode;

} else if (code == end_code) {

int count;

unsigned char buf[260];

if (ZeroDataBlock)

return -2;

while ((count = GetDataBlock(src, buf)) > 0)

;

if (count != 0) {

/*

* pm_message("missing EOD in data stream (common occurence)");

*/

}

return -2;

}

incode = code;

if (code >= max_code) {

*sp++ = firstcode;

code = oldcode;

}

while (code >= clear_code) {

*sp++ = table[1][code];

if (code == table[0][code])

RWSetMsg("circular table entry BIG ERROR");

code = table[0][code];

}

*sp++ = firstcode = table[1][code];

if ((code = max_code) < (1 << MAX_LWZ_BITS)) {

table[0][code] = oldcode;

table[1][code] = firstcode;

++max_code;

if ((max_code >= max_code_size) &&

(max_code_size < (1 << MAX_LWZ_BITS))) {

max_code_size *= 2;

++code_size;

}

}

oldcode = incode;

if (sp > stack)

return *--sp;

}

return code;

}

static Image *

ReadImage(SDL_RWops * src, int len, int height, int cmapSize,

unsigned char cmap[3][MAXCOLORMAPSIZE],

int gray, int interlace, int ignore)

{

Image *image;

unsigned char c;

int i, v;

int xpos = 0, ypos = 0, pass = 0;

/*

** Initialize the compression routines

*/

if (!ReadOK(src, &c, 1)) {

RWSetMsg("EOF / read error on image data");

return NULL;

}

if (LWZReadByte(src, TRUE, c) < 0) {

RWSetMsg("error reading image");

return NULL;

}

/*

** If this is an "uninteresting picture" ignore it.

*/

if (ignore) {

while (LWZReadByte(src, FALSE, c) >= 0)

;

return NULL;

}

image = ImageNewCmap(len, height, cmapSize);

for (i = 0; i < cmapSize; i++)

ImageSetCmap(image, i, cmap[CM_RED][i],

cmap[CM_GREEN][i], cmap[CM_BLUE][i]);

while ((v = LWZReadByte(src, FALSE, c)) >= 0) {

#ifdef USED_BY_SDL

((Uint8 *)image->pixels)[xpos + ypos * image->pitch] = v;

#else

image->data[xpos + ypos * len] = v;

#endif

++xpos;

if (xpos == len) {

xpos = 0;

if (interlace) {

switch (pass) {

case 0:

case 1:

ypos += 8;

break;

case 2:

ypos += 4;

break;

case 3:

ypos += 2;

break;

}

if (ypos >= height) {

++pass;

switch (pass) {

case 1:

ypos = 4;

break;

case 2:

ypos = 2;

break;

case 3:

ypos = 1;

break;

default:

goto fini;

}

}

} else {

++ypos;

}

}

if (ypos >= height)

break;

}

fini:

return image;

}

#else

/* See if an image is contained in a data source */

int IMG_isGIF(SDL_RWops *src)

{

return(0);

}

/* Load a GIF type image from an SDL datasource */

SDL_Surface *IMG_LoadGIF_RW(SDL_RWops *src)

{

return(NULL);

}

#endif /* LOAD_GIF */

#endif /* !defined(__APPLE__) || defined(SDL_IMAGE_USE_COMMON_BACKEND) */