IMG_bmp.c

/*
  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.
*/

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

/* This is a BMP image file loading framework
 *
 * ICO/CUR file support is here as well since it uses similar internal
 * representation
 *
 * A good test suite of BMP images is available at:
 * http://entropymine.com/jason/bmpsuite/bmpsuite/html/bmpsuite.html
 */

#include "SDL_image.h"

#ifdef LOAD_BMP

/* See if an image is contained in a data source */
int IMG_isBMP(SDL_RWops *src)
{
    Sint64 start;
    int is_BMP;
    char magic[2];

    if ( !src )
        return 0;
    start = SDL_RWtell(src);
    is_BMP = 0;
    if ( SDL_RWread(src, magic, sizeof(magic), 1) ) {
        if ( SDL_strncmp(magic, "BM", 2) == 0 ) {
            is_BMP = 1;
        }
    }
    SDL_RWseek(src, start, RW_SEEK_SET);
    return(is_BMP);
}

static int IMG_isICOCUR(SDL_RWops *src, int type)
{
    Sint64 start;
    int is_ICOCUR;

    /* The Win32 ICO file header (14 bytes) */
    Uint16 bfReserved;
    Uint16 bfType;
    Uint16 bfCount;

    if ( !src )
        return 0;
    start = SDL_RWtell(src);
    is_ICOCUR = 0;
    bfReserved = SDL_ReadLE16(src);
    bfType = SDL_ReadLE16(src);
    bfCount = SDL_ReadLE16(src);
    if ((bfReserved == 0) && (bfType == type) && (bfCount != 0))
        is_ICOCUR = 1;
    SDL_RWseek(src, start, RW_SEEK_SET);

    return (is_ICOCUR);
}

int IMG_isICO(SDL_RWops *src)
{
    return IMG_isICOCUR(src, 1);
}

int IMG_isCUR(SDL_RWops *src)
{
    return IMG_isICOCUR(src, 2);
}

#include "SDL_error.h"
#include "SDL_video.h"
#include "SDL_endian.h"

/* Compression encodings for BMP files */
#ifndef BI_RGB
#define BI_RGB      0
#define BI_RLE8     1
#define BI_RLE4     2
#define BI_BITFIELDS    3
#endif

static int readRlePixels(SDL_Surface * surface, SDL_RWops * src, int isRle8)
{
    /*
    | Sets the surface pixels from src.  A bmp image is upside down.
    */
    int pitch = surface->pitch;
    int height = surface->h;
    Uint8 *start = (Uint8 *)surface->pixels;
    Uint8 *end = start + (height*pitch);
    Uint8 *bits = end-pitch, *spot;
    int ofs = 0;
    Uint8 ch;
    Uint8 needsPad;

#define COPY_PIXEL(x)   spot = &bits[ofs++]; if(spot >= start && spot < end) *spot = (x)

    for (;;) {
        if ( !SDL_RWread(src, &ch, 1, 1) ) return 1;
        /*
        | encoded mode starts with a run length, and then a byte
        | with two colour indexes to alternate between for the run
        */
        if ( ch ) {
            Uint8 pixel;
            if ( !SDL_RWread(src, &pixel, 1, 1) ) return 1;
            if ( isRle8 ) {                 /* 256-color bitmap, compressed */
                do {
                    COPY_PIXEL(pixel);
                } while (--ch);
            } else {                         /* 16-color bitmap, compressed */
                Uint8 pixel0 = pixel >> 4;
                Uint8 pixel1 = pixel & 0x0F;
                for (;;) {
                    COPY_PIXEL(pixel0); /* even count, high nibble */
                    if (!--ch) break;
                    COPY_PIXEL(pixel1); /* odd count, low nibble */
                    if (!--ch) break;
                }
            }
        } else {
            /*
            | A leading zero is an escape; it may signal the end of the bitmap,
            | a cursor move, or some absolute data.
            | zero tag may be absolute mode or an escape
            */
            if ( !SDL_RWread(src, &ch, 1, 1) ) return 1;
            switch (ch) {
            case 0:                         /* end of line */
                ofs = 0;
                bits -= pitch;               /* go to previous */
                break;
            case 1:                         /* end of bitmap */
                return 0;                    /* success! */
            case 2:                         /* delta */
                if ( !SDL_RWread(src, &ch, 1, 1) ) return 1;
                ofs += ch;
                if ( !SDL_RWread(src, &ch, 1, 1) ) return 1;
                bits -= (ch * pitch);
                break;
            default:                        /* no compression */
                if (isRle8) {
                    needsPad = ( ch & 1 );
                    do {
                        Uint8 pixel;
                        if ( !SDL_RWread(src, &pixel, 1, 1) ) return 1;
                        COPY_PIXEL(pixel);
                    } while (--ch);
                } else {
                    needsPad = ( ((ch+1)>>1) & 1 ); /* (ch+1)>>1: bytes size */
                    for (;;) {
                        Uint8 pixel;
                        if ( !SDL_RWread(src, &pixel, 1, 1) ) return 1;
                        COPY_PIXEL(pixel >> 4);
                        if (!--ch) break;
                        COPY_PIXEL(pixel & 0x0F);
                        if (!--ch) break;
                    }
                }
                /* pad at even boundary */
                if ( needsPad && !SDL_RWread(src, &ch, 1, 1) ) return 1;
                break;
            }
        }
    }
}

static void CorrectAlphaChannel(SDL_Surface *surface)
{
    /* Check to see if there is any alpha channel data */
    SDL_bool hasAlpha = SDL_FALSE;
#if SDL_BYTEORDER == SDL_BIG_ENDIAN
    int alphaChannelOffset = 0;
#else
    int alphaChannelOffset = 3;
#endif
    Uint8 *alpha = ((Uint8*)surface->pixels) + alphaChannelOffset;
    Uint8 *end = alpha + surface->h * surface->pitch;

    while (alpha < end) {
        if (*alpha != 0) {
            hasAlpha = SDL_TRUE;
            break;
        }
        alpha += 4;
    }

    if (!hasAlpha) {
        alpha = ((Uint8*)surface->pixels) + alphaChannelOffset;
        while (alpha < end) {
            *alpha = SDL_ALPHA_OPAQUE;
            alpha += 4;
        }
    }
}

static SDL_Surface *LoadBMP_RW (SDL_RWops *src, int freesrc)
{
    SDL_bool was_error;
    Sint64 fp_offset;
    int bmpPitch;
    int i, pad;
    SDL_Surface *surface;
    Uint32 Rmask = 0;
    Uint32 Gmask = 0;
    Uint32 Bmask = 0;
    Uint32 Amask = 0;
    SDL_Palette *palette;
    Uint8 *bits;
    Uint8 *top, *end;
    SDL_bool topDown;
    int ExpandBMP;
    SDL_bool haveRGBMasks = SDL_FALSE;
    SDL_bool haveAlphaMask = SDL_FALSE;
    SDL_bool correctAlpha = SDL_FALSE;

    /* The Win32 BMP file header (14 bytes) */
    char   magic[2];
    Uint32 bfSize;
    Uint16 bfReserved1;
    Uint16 bfReserved2;
    Uint32 bfOffBits;

    /* The Win32 BITMAPINFOHEADER struct (40 bytes) */
    Uint32 biSize;
    Sint32 biWidth;
    Sint32 biHeight = 0;
    Uint16 biPlanes;
    Uint16 biBitCount;
    Uint32 biCompression;
    Uint32 biSizeImage;
    Sint32 biXPelsPerMeter;
    Sint32 biYPelsPerMeter;
    Uint32 biClrUsed;
    Uint32 biClrImportant;

    /* Make sure we are passed a valid data source */
    surface = NULL;
    was_error = SDL_FALSE;
    if ( src == NULL ) {
        was_error = SDL_TRUE;
        goto done;
    }

    /* Read in the BMP file header */
    fp_offset = SDL_RWtell(src);
    SDL_ClearError();
    if ( SDL_RWread(src, magic, 1, 2) != 2 ) {
        SDL_Error(SDL_EFREAD);
        was_error = SDL_TRUE;
        goto done;
    }
    if ( SDL_strncmp(magic, "BM", 2) != 0 ) {
        IMG_SetError("File is not a Windows BMP file");
        was_error = SDL_TRUE;
        goto done;
    }
    bfSize      = SDL_ReadLE32(src);
    bfReserved1 = SDL_ReadLE16(src);
    bfReserved2 = SDL_ReadLE16(src);
    bfOffBits   = SDL_ReadLE32(src);

    /* Read the Win32 BITMAPINFOHEADER */
    biSize      = SDL_ReadLE32(src);
    if ( biSize == 12 ) {   /* really old BITMAPCOREHEADER */
        biWidth     = (Uint32)SDL_ReadLE16(src);
        biHeight    = (Uint32)SDL_ReadLE16(src);
        biPlanes    = SDL_ReadLE16(src);
        biBitCount  = SDL_ReadLE16(src);
        biCompression   = BI_RGB;
        biSizeImage = 0;
        biXPelsPerMeter = 0;
        biYPelsPerMeter = 0;
        biClrUsed   = 0;
        biClrImportant  = 0;
    } else if (biSize >= 40) {  /* some version of BITMAPINFOHEADER */
        Uint32 headerSize;
        biWidth     = SDL_ReadLE32(src);
        biHeight    = SDL_ReadLE32(src);
        biPlanes    = SDL_ReadLE16(src);
        biBitCount  = SDL_ReadLE16(src);
        biCompression   = SDL_ReadLE32(src);
        biSizeImage = SDL_ReadLE32(src);
        biXPelsPerMeter = SDL_ReadLE32(src);
        biYPelsPerMeter = SDL_ReadLE32(src);
        biClrUsed   = SDL_ReadLE32(src);
        biClrImportant  = SDL_ReadLE32(src);

        /* 64 == BITMAPCOREHEADER2, an incompatible OS/2 2.x extension. Skip this stuff for now. */
        if (biSize != 64) {
            /* This is complicated. If compression is BI_BITFIELDS, then
               we have 3 DWORDS that specify the RGB masks. This is either
               stored here in an BITMAPV2INFOHEADER (which only differs in
               that it adds these RGB masks) and biSize >= 52, or we've got
               these masks stored in the exact same place, but strictly
               speaking, this is the bmiColors field in BITMAPINFO immediately
               following the legacy v1 info header, just past biSize. */
            if (biCompression == BI_BITFIELDS) {
                haveRGBMasks = SDL_TRUE;
                Rmask = SDL_ReadLE32(src);
                Gmask = SDL_ReadLE32(src);
                Bmask = SDL_ReadLE32(src);

                /* ...v3 adds an alpha mask. */
                if (biSize >= 56) {  /* BITMAPV3INFOHEADER; adds alpha mask */
                    haveAlphaMask = SDL_TRUE;
                    Amask = SDL_ReadLE32(src);
                }
            } else {
                /* the mask fields are ignored for v2+ headers if not BI_BITFIELD. */
                if (biSize >= 52) {  /* BITMAPV2INFOHEADER; adds RGB masks */
                    /*Rmask = */ SDL_ReadLE32(src);
                    /*Gmask = */ SDL_ReadLE32(src);
                    /*Bmask = */ SDL_ReadLE32(src);
                }
                if (biSize >= 56) {  /* BITMAPV3INFOHEADER; adds alpha mask */
                    /*Amask = */ SDL_ReadLE32(src);
                }
            }

            /* Insert other fields here; Wikipedia and MSDN say we're up to
               v5 of this header, but we ignore those for now (they add gamma,
               color spaces, etc). Ignoring the weird OS/2 2.x format, we
               currently parse up to v3 correctly (hopefully!). */
        }

        /* skip any header bytes we didn't handle... */
        headerSize = (Uint32) (SDL_RWtell(src) - (fp_offset + 14));
        if (biSize > headerSize) {
            SDL_RWseek(src, (biSize - headerSize), RW_SEEK_CUR);
        }
    }
    if (biHeight < 0) {
        topDown = SDL_TRUE;
        biHeight = -biHeight;
    } else {
        topDown = SDL_FALSE;
    }

    /* Check for read error */
    if (SDL_strcmp(SDL_GetError(), "") != 0) {
        was_error = SDL_TRUE;
        goto done;
    }

    /* Expand 1 and 4 bit bitmaps to 8 bits per pixel */
    switch (biBitCount) {
        case 1:
        case 4:
            ExpandBMP = biBitCount;
            biBitCount = 8;
            break;
        default:
            ExpandBMP = 0;
            break;
    }

    /* RLE4 and RLE8 BMP compression is supported */
    switch (biCompression) {
        case BI_RGB:
            /* If there are no masks, use the defaults */
            SDL_assert(!haveRGBMasks);
            SDL_assert(!haveAlphaMask);
            /* Default values for the BMP format */
            switch (biBitCount) {
            case 15:
            case 16:
                Rmask = 0x7C00;
                Gmask = 0x03E0;
                Bmask = 0x001F;
                break;
            case 24:
#if SDL_BYTEORDER == SDL_BIG_ENDIAN
                Rmask = 0x000000FF;
                Gmask = 0x0000FF00;
                Bmask = 0x00FF0000;
#else
                Rmask = 0x00FF0000;
                Gmask = 0x0000FF00;
                Bmask = 0x000000FF;
#endif
                break;
            case 32:
                /* We don't know if this has alpha channel or not */
                correctAlpha = SDL_TRUE;
                Amask = 0xFF000000;
                Rmask = 0x00FF0000;
                Gmask = 0x0000FF00;
                Bmask = 0x000000FF;
                break;
            default:
                break;
            }
            break;

        case BI_BITFIELDS:
            break;  /* we handled this in the info header. */

        default:
            break;
    }

    /* Create a compatible surface, note that the colors are RGB ordered */
    surface = SDL_CreateRGBSurface(SDL_SWSURFACE,
            biWidth, biHeight, biBitCount, Rmask, Gmask, Bmask, Amask);
    if ( surface == NULL ) {
        was_error = SDL_TRUE;
        goto done;
    }

    /* Load the palette, if any */
    palette = (surface->format)->palette;
    if ( palette ) {
        if ( SDL_RWseek(src, fp_offset+14+biSize, RW_SEEK_SET) < 0 ) {
            SDL_Error(SDL_EFSEEK);
            was_error = SDL_TRUE;
            goto done;
        }

        /*
        | guich: always use 1<<bpp b/c some bitmaps can bring wrong information
        | for colorsUsed
        */
        /* if ( biClrUsed == 0 ) {  */
        biClrUsed = 1 << biBitCount;
        /* } */
        if ( biSize == 12 ) {
            for ( i = 0; i < (int)biClrUsed; ++i ) {
                SDL_RWread(src, &palette->colors[i].b, 1, 1);
                SDL_RWread(src, &palette->colors[i].g, 1, 1);
                SDL_RWread(src, &palette->colors[i].r, 1, 1);
                palette->colors[i].a = SDL_ALPHA_OPAQUE;
            }
        } else {
            for ( i = 0; i < (int)biClrUsed; ++i ) {
                SDL_RWread(src, &palette->colors[i].b, 1, 1);
                SDL_RWread(src, &palette->colors[i].g, 1, 1);
                SDL_RWread(src, &palette->colors[i].r, 1, 1);
                SDL_RWread(src, &palette->colors[i].a, 1, 1);

                /* According to Microsoft documentation, the fourth element
                   is reserved and must be zero, so we shouldn't treat it as
                   alpha.
                */
                palette->colors[i].a = SDL_ALPHA_OPAQUE;
            }
        }
        palette->ncolors = biClrUsed;
    }

    /* Read the surface pixels.  Note that the bmp image is upside down */
    if ( SDL_RWseek(src, fp_offset+bfOffBits, RW_SEEK_SET) < 0 ) {
        SDL_Error(SDL_EFSEEK);
        was_error = SDL_TRUE;
        goto done;
    }
    if ((biCompression == BI_RLE4) || (biCompression == BI_RLE8)) {
        was_error = (SDL_bool)readRlePixels(surface, src, biCompression == BI_RLE8);
        if (was_error) IMG_SetError("Error reading from BMP");
        goto done;
    }
    top = (Uint8 *)surface->pixels;
    end = (Uint8 *)surface->pixels+(surface->h*surface->pitch);
    switch (ExpandBMP) {
        case 1:
            bmpPitch = (biWidth + 7) >> 3;
            pad  = (((bmpPitch)%4) ? (4-((bmpPitch)%4)) : 0);
            break;
        case 4:
            bmpPitch = (biWidth + 1) >> 1;
            pad  = (((bmpPitch)%4) ? (4-((bmpPitch)%4)) : 0);
            break;
        default:
            pad  = ((surface->pitch%4) ?
                    (4-(surface->pitch%4)) : 0);
            break;
    }
    if ( topDown ) {
        bits = top;
    } else {
        bits = end - surface->pitch;
    }
    while ( bits >= top && bits < end ) {
        switch (ExpandBMP) {
            case 1:
            case 4: {
            Uint8 pixel = 0;
            int   shift = (8-ExpandBMP);
            for ( i=0; i<surface->w; ++i ) {
                if ( i%(8/ExpandBMP) == 0 ) {
                    if ( !SDL_RWread(src, &pixel, 1, 1) ) {
                        IMG_SetError("Error reading from BMP");
                        was_error = SDL_TRUE;
                        goto done;
                    }
                }
                *(bits+i) = (pixel>>shift);
                pixel <<= ExpandBMP;
            } }
            break;

            default:
            if ( SDL_RWread(src, bits, 1, surface->pitch) != surface->pitch ) {
                SDL_Error(SDL_EFREAD);
                was_error = SDL_TRUE;
                goto done;
            }
#if SDL_BYTEORDER == SDL_BIG_ENDIAN
            /* Byte-swap the pixels if needed. Note that the 24bpp
               case has already been taken care of above. */
            switch(biBitCount) {
                case 15:
                case 16: {
                    Uint16 *pix = (Uint16 *)bits;
                    for(i = 0; i < surface->w; i++)
                        pix[i] = SDL_Swap16(pix[i]);
                    break;
                }

                case 32: {
                    Uint32 *pix = (Uint32 *)bits;
                    for(i = 0; i < surface->w; i++)
                        pix[i] = SDL_Swap32(pix[i]);
                    break;
                }
            }
#endif
            break;
        }
        /* Skip padding bytes, ugh */
        if ( pad ) {
            Uint8 padbyte;
            for ( i=0; i<pad; ++i ) {
                SDL_RWread(src, &padbyte, 1, 1);
            }
        }
        if ( topDown ) {
            bits += surface->pitch;
        } else {
            bits -= surface->pitch;
        }
    }
    if (correctAlpha) {
        CorrectAlphaChannel(surface);
    }
done:
    if ( was_error ) {
        if ( src ) {
            SDL_RWseek(src, fp_offset, RW_SEEK_SET);
        }
        if ( surface ) {
            SDL_FreeSurface(surface);
        }
        surface = NULL;
    }
    if ( freesrc && src ) {
        SDL_RWclose(src);
    }
    return(surface);
}

static Uint8
SDL_Read8(SDL_RWops * src)
{
    Uint8 value;

    SDL_RWread(src, &value, 1, 1);
    return (value);
}

static SDL_Surface *
LoadICOCUR_RW(SDL_RWops * src, int type, int freesrc)
{
    SDL_bool was_error;
    Sint64 fp_offset;
    int bmpPitch;
    int i, pad;
    SDL_Surface *surface;
    Uint32 Rmask;
    Uint32 Gmask;
    Uint32 Bmask;
    Uint8 *bits;
    int ExpandBMP;
    int maxCol = 0;
    int icoOfs = 0;
    Uint32 palette[256];

    /* The Win32 ICO file header (14 bytes) */
    Uint16 bfReserved;
    Uint16 bfType;
    Uint16 bfCount;

    /* The Win32 BITMAPINFOHEADER struct (40 bytes) */
    Uint32 biSize;
    Sint32 biWidth;
    Sint32 biHeight;
    Uint16 biPlanes;
    Uint16 biBitCount;
    Uint32 biCompression;
    Uint32 biSizeImage;
    Sint32 biXPelsPerMeter;
    Sint32 biYPelsPerMeter;
    Uint32 biClrUsed;
    Uint32 biClrImportant;

    /* Make sure we are passed a valid data source */
    surface = NULL;
    was_error = SDL_FALSE;
    if (src == NULL) {
        was_error = SDL_TRUE;
        goto done;
    }

    /* Read in the ICO file header */
    fp_offset = SDL_RWtell(src);
    SDL_ClearError();

    bfReserved = SDL_ReadLE16(src);
    bfType = SDL_ReadLE16(src);
    bfCount = SDL_ReadLE16(src);
    if ((bfReserved != 0) || (bfType != type) || (bfCount == 0)) {
        IMG_SetError("File is not a Windows %s file", type == 1 ? "ICO" : "CUR");
        was_error = SDL_TRUE;
        goto done;
    }

    /* Read the Win32 Icon Directory */
    for (i = 0; i < bfCount; i++) {
        /* Icon Directory Entries */
        int bWidth = SDL_Read8(src);    /* Uint8, but 0 = 256 ! */
        int bHeight = SDL_Read8(src);   /* Uint8, but 0 = 256 ! */
        int bColorCount = SDL_Read8(src);       /* Uint8, but 0 = 256 ! */
        Uint8 bReserved = SDL_Read8(src);
        Uint16 wPlanes = SDL_ReadLE16(src);
        Uint16 wBitCount = SDL_ReadLE16(src);
        Uint32 dwBytesInRes = SDL_ReadLE32(src);
        Uint32 dwImageOffset = SDL_ReadLE32(src);

        if (!bWidth)
            bWidth = 256;
        if (!bHeight)
            bHeight = 256;
        if (!bColorCount)
            bColorCount = 256;

        //printf("%dx%d@%d - %08x\n", bWidth, bHeight, bColorCount, dwImageOffset);
        if (bColorCount > maxCol) {
            maxCol = bColorCount;
            icoOfs = dwImageOffset;
            //printf("marked\n");
        }
    }

    /* Advance to the DIB Data */
    if (SDL_RWseek(src, icoOfs, RW_SEEK_SET) < 0) {
        SDL_Error(SDL_EFSEEK);
        was_error = SDL_TRUE;
        goto done;
    }

    /* Read the Win32 BITMAPINFOHEADER */
    biSize = SDL_ReadLE32(src);
    if (biSize == 40) {
        biWidth = SDL_ReadLE32(src);
        biHeight = SDL_ReadLE32(src);
        biPlanes = SDL_ReadLE16(src);
        biBitCount = SDL_ReadLE16(src);
        biCompression = SDL_ReadLE32(src);
        biSizeImage = SDL_ReadLE32(src);
        biXPelsPerMeter = SDL_ReadLE32(src);
        biYPelsPerMeter = SDL_ReadLE32(src);
        biClrUsed = SDL_ReadLE32(src);
        biClrImportant = SDL_ReadLE32(src);
    } else {
        IMG_SetError("Unsupported ICO bitmap format");
        was_error = SDL_TRUE;
        goto done;
    }

    /* Check for read error */
    if (SDL_strcmp(SDL_GetError(), "") != 0) {
        was_error = SDL_TRUE;
        goto done;
    }

    /* We don't support any BMP compression right now */
    switch (biCompression) {
    case BI_RGB:
        /* Default values for the BMP format */
        switch (biBitCount) {
        case 1:
        case 4:
            ExpandBMP = biBitCount;
            biBitCount = 8;
            break;
        case 8:
            ExpandBMP = 8;
            break;
        case 32:
            Rmask = 0x00FF0000;
            Gmask = 0x0000FF00;
            Bmask = 0x000000FF;
            ExpandBMP = 0;
            break;
        default:
            IMG_SetError("ICO file with unsupported bit count");
            was_error = SDL_TRUE;
            goto done;
        }
        break;
    default:
        IMG_SetError("Compressed ICO files not supported");
        was_error = SDL_TRUE;
        goto done;
    }

    /* sanity check image size, so we don't overflow integers, etc. */
    if ((biWidth < 0) || (biWidth > 0xFFFFFF) ||
        (biHeight < 0) || (biHeight > 0xFFFFFF)) {
        IMG_SetError("Unsupported or invalid ICO dimensions");
        was_error = SDL_TRUE;
        goto done;
    }

    /* Create a RGBA surface */
    biHeight = biHeight >> 1;
    //printf("%d x %d\n", biWidth, biHeight);
    surface =
        SDL_CreateRGBSurface(0, biWidth, biHeight, 32, 0x00FF0000,
                             0x0000FF00, 0x000000FF, 0xFF000000);
    if (surface == NULL) {
        was_error = SDL_TRUE;
        goto done;
    }

    /* Load the palette, if any */
    //printf("bc %d bused %d\n", biBitCount, biClrUsed);
    if (biBitCount <= 8) {
        if (biClrUsed == 0) {
            biClrUsed = 1 << biBitCount;
        }
        if (biClrUsed > SDL_arraysize(palette)) {
            IMG_SetError("Unsupported or incorrect biClrUsed field");
            was_error = SDL_TRUE;
            goto done;
        }
        for (i = 0; i < (int) biClrUsed; ++i) {
            SDL_RWread(src, &palette[i], 4, 1);
        }
    }

    /* Read the surface pixels.  Note that the bmp image is upside down */
    bits = (Uint8 *) surface->pixels + (surface->h * surface->pitch);
    switch (ExpandBMP) {
    case 1:
        bmpPitch = (biWidth + 7) >> 3;
        pad = (((bmpPitch) % 4) ? (4 - ((bmpPitch) % 4)) : 0);
        break;
    case 4:
        bmpPitch = (biWidth + 1) >> 1;
        pad = (((bmpPitch) % 4) ? (4 - ((bmpPitch) % 4)) : 0);
        break;
    case 8:
        bmpPitch = biWidth;
        pad = (((bmpPitch) % 4) ? (4 - ((bmpPitch) % 4)) : 0);
        break;
    default:
        bmpPitch = biWidth * 4;
        pad = 0;
        break;
    }
    while (bits > (Uint8 *) surface->pixels) {
        bits -= surface->pitch;
        switch (ExpandBMP) {
        case 1:
        case 4:
        case 8:
            {
                Uint8 pixel = 0;
                int shift = (8 - ExpandBMP);
                for (i = 0; i < surface->w; ++i) {
                    if (i % (8 / ExpandBMP) == 0) {
                        if (!SDL_RWread(src, &pixel, 1, 1)) {
                            IMG_SetError("Error reading from ICO");
                            was_error = SDL_TRUE;
                            goto done;
                        }
                    }
                    *((Uint32 *) bits + i) = (palette[pixel >> shift]);
                    pixel <<= ExpandBMP;
                }
            }
            break;

        default:
            if (SDL_RWread(src, bits, 1, surface->pitch)
                != surface->pitch) {
                SDL_Error(SDL_EFREAD);
                was_error = SDL_TRUE;
                goto done;
            }
            break;
        }
        /* Skip padding bytes, ugh */
        if (pad) {
            Uint8 padbyte;
            for (i = 0; i < pad; ++i) {
                SDL_RWread(src, &padbyte, 1, 1);
            }
        }
    }
    /* Read the mask pixels.  Note that the bmp image is upside down */
    bits = (Uint8 *) surface->pixels + (surface->h * surface->pitch);
    ExpandBMP = 1;
    bmpPitch = (biWidth + 7) >> 3;
    pad = (((bmpPitch) % 4) ? (4 - ((bmpPitch) % 4)) : 0);
    while (bits > (Uint8 *) surface->pixels) {
        Uint8 pixel = 0;
        int shift = (8 - ExpandBMP);

        bits -= surface->pitch;
        for (i = 0; i < surface->w; ++i) {
            if (i % (8 / ExpandBMP) == 0) {
                if (!SDL_RWread(src, &pixel, 1, 1)) {
                    IMG_SetError("Error reading from ICO");
                    was_error = SDL_TRUE;
                    goto done;
                }
            }
            *((Uint32 *) bits + i) |= ((pixel >> shift) ? 0 : 0xFF000000);
            pixel <<= ExpandBMP;
        }
        /* Skip padding bytes, ugh */
        if (pad) {
            Uint8 padbyte;
            for (i = 0; i < pad; ++i) {
                SDL_RWread(src, &padbyte, 1, 1);
            }
        }
    }
  done:
    if (was_error) {
        if (src) {
            SDL_RWseek(src, fp_offset, RW_SEEK_SET);
        }
        if (surface) {
            SDL_FreeSurface(surface);
        }
        surface = NULL;
    }
    if (freesrc && src) {
        SDL_RWclose(src);
    }
    return (surface);
}

/* Load a BMP type image from an SDL datasource */
SDL_Surface *IMG_LoadBMP_RW(SDL_RWops *src)
{
    return(LoadBMP_RW(src, 0));
}

/* Load a ICO type image from an SDL datasource */
SDL_Surface *IMG_LoadICO_RW(SDL_RWops *src)
{
    return(LoadICOCUR_RW(src, 1, 0));
}

/* Load a CUR type image from an SDL datasource */
SDL_Surface *IMG_LoadCUR_RW(SDL_RWops *src)
{
    return(LoadICOCUR_RW(src, 2, 0));
}

#else

/* See if an image is contained in a data source */
int IMG_isBMP(SDL_RWops *src)
{
    return(0);
}

int IMG_isICO(SDL_RWops *src)
{
    return(0);
}

int IMG_isCUR(SDL_RWops *src)
{
    return(0);
}

/* Load a BMP type image from an SDL datasource */
SDL_Surface *IMG_LoadBMP_RW(SDL_RWops *src)
{
    return(NULL);
}

/* Load a BMP type image from an SDL datasource */
SDL_Surface *IMG_LoadCUR_RW(SDL_RWops *src)
{
    return(NULL);
}

/* Load a BMP type image from an SDL datasource */
SDL_Surface *IMG_LoadICO_RW(SDL_RWops *src)
{
    return(NULL);
}

#endif /* LOAD_BMP */

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