gd_bmp.c

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/*
    gd_bmp.c
 
    Bitmap format support for libgd
 
    * Written 2007, Scott MacVicar
    ---------------------------------------------------------------------------
 
    Todo:
 
    Bitfield encoding
 
    ----------------------------------------------------------------------------
 */
/* $Id$ */
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
 
#include <stdio.h>
#include <math.h>
#include <string.h>
#include <stdlib.h>
#include "gd.h"
#include "gdhelpers.h"
#include "bmp.h"
 
static int compress_row(unsigned char *uncompressed_row, int length);
static int build_rle_packet(unsigned char *row, int packet_type, int length, unsigned char *data);
 
static int bmp_read_header(gdIOCtxPtr infile, bmp_hdr_t *hdr);
static int bmp_read_info(gdIOCtxPtr infile, bmp_info_t *info);
static int bmp_read_windows_v3_info(gdIOCtxPtr infile, bmp_info_t *info);
static int bmp_read_os2_v1_info(gdIOCtxPtr infile, bmp_info_t *info);
static int bmp_read_os2_v2_info(gdIOCtxPtr infile, bmp_info_t *info);
 
static int bmp_read_direct(gdImagePtr im, gdIOCtxPtr infile, bmp_info_t *info, bmp_hdr_t *header);
static int bmp_read_1bit(gdImagePtr im, gdIOCtxPtr infile, bmp_info_t *info, bmp_hdr_t *header);
static int bmp_read_4bit(gdImagePtr im, gdIOCtxPtr infile, bmp_info_t *info, bmp_hdr_t *header);
static int bmp_read_8bit(gdImagePtr im, gdIOCtxPtr infile, bmp_info_t *info, bmp_hdr_t *header);
static int bmp_read_rle(gdImagePtr im, gdIOCtxPtr infile, bmp_info_t *info);
 
#define BMP_DEBUG(s)
 
static int gdBMPPutWord(gdIOCtx *out, int w)
{
    /* Byte order is little-endian */
    gdPutC(w & 0xFF, out);
    gdPutC((w >> 8) & 0xFF, out);
    return 0;
}
 
static int gdBMPPutInt(gdIOCtx *out, int w)
{
    /* Byte order is little-endian */
    gdPutC(w & 0xFF, out);
    gdPutC((w >> 8) & 0xFF, out);
    gdPutC((w >> 16) & 0xFF, out);
    gdPutC((w >> 24) & 0xFF, out);
    return 0;
}
 
/*
    Function: gdImageBmpPtr
*/
void * gdImageBmpPtr(gdImagePtr im, int *size, int compression)
{
    void *rv;
    gdIOCtx *out = gdNewDynamicCtx(2048, NULL);
    if (out == NULL) return NULL;
    gdImageBmpCtx(im, out, compression);
    rv = gdDPExtractData(out, size);
    out->gd_free(out);
    return rv;
}
 
/*
    Function: gdImageBmp
*/
void gdImageBmp(gdImagePtr im, FILE *outFile, int compression)
{
    gdIOCtx *out = gdNewFileCtx(outFile);
    if (out == NULL) return;
    gdImageBmpCtx(im, out, compression);
    out->gd_free(out);
}
 
/*
    Function: gdImageBmpCtx
*/
void gdImageBmpCtx(gdImagePtr im, gdIOCtxPtr out, int compression)
{
    int bitmap_size = 0, info_size, total_size, padding;
    int i, row, xpos, pixel;
    int error = 0;
    unsigned char *uncompressed_row = NULL, *uncompressed_row_start = NULL;
    FILE *tmpfile_for_compression = NULL;
    gdIOCtxPtr out_original = NULL;
 
    /* No compression if its true colour or we don't support seek */
    if (im->trueColor) {
        compression = 0;
    }
 
    if (compression == 1 && !out->seek) {
        /* Try to create a temp file where we can seek */
        if ((tmpfile_for_compression = tmpfile()) == NULL) {
            compression = 0;
        } else {
            out_original = out;
            if ((out = (gdIOCtxPtr)gdNewFileCtx(tmpfile_for_compression)) == NULL) {
                out = out_original;
                out_original = NULL;
                compression = 0;
            }
        }
    }
 
    bitmap_size = ((im->sx * (im->trueColor ? 24 : 8)) / 8) * im->sy;
 
    /* 40 byte Windows v3 header */
    info_size = BMP_WINDOWS_V3;
 
    /* data for the palette */
    if (!im->trueColor) {
        info_size += im->colorsTotal * 4;
        if (compression) {
            bitmap_size = 0;
        }
    }
 
    /* bitmap header + info header + data */
    total_size = 14 + info_size + bitmap_size;
 
    /* write bmp header info */
    gdPutBuf("BM", 2, out);
    gdBMPPutInt(out, total_size);
    gdBMPPutWord(out, 0);
    gdBMPPutWord(out, 0);
    gdBMPPutInt(out, 14 + info_size);
 
    /* write Windows v3 headers */
    gdBMPPutInt(out, BMP_WINDOWS_V3); /* header size */
    gdBMPPutInt(out, im->sx); /* width */
    gdBMPPutInt(out, im->sy); /* height */
    gdBMPPutWord(out, 1); /* colour planes */
    gdBMPPutWord(out, (im->trueColor ? 24 : 8)); /* bit count */
    gdBMPPutInt(out, (compression ? BMP_BI_RLE8 : BMP_BI_RGB)); /* compression */
    gdBMPPutInt(out, bitmap_size); /* image size */
    gdBMPPutInt(out, 0); /* H resolution */
    gdBMPPutInt(out, 0); /* V ressolution */
    gdBMPPutInt(out, im->colorsTotal); /* colours used */
    gdBMPPutInt(out, 0); /* important colours */
 
    /* The line must be divisible by 4, else it's padded with NULLs */
    padding = ((int)(im->trueColor ? 3 : 1) * im->sx) % 4;
    if (padding) {
        padding = 4 - padding;
    }
 
    /* 8-bit colours */
    if (!im->trueColor) {
        for(i = 0; i< im->colorsTotal; ++i) {
            Putchar(gdImageBlue(im, i), out);
            Putchar(gdImageGreen(im, i), out);
            Putchar(gdImageRed(im, i), out);
            Putchar(0, out);
        }
 
        if (compression) {
            /* Can potentially change this to X + ((X / 128) * 3) */
            uncompressed_row = uncompressed_row_start = (unsigned char *) gdCalloc(gdImageSX(im) * 2, sizeof(char));
            if (!uncompressed_row) {
                /* malloc failed */
                goto cleanup;
            }
        }
 
        for (row = (im->sy - 1); row >= 0; row--) {
            if (compression) {
                memset (uncompressed_row, 0, gdImageSX(im));
            }
 
            for (xpos = 0; xpos < im->sx; xpos++) {
                if (compression) {
                    *uncompressed_row++ = (unsigned char)gdImageGetPixel(im, xpos, row);
                } else {
                    Putchar(gdImageGetPixel(im, xpos, row), out);
                }
            }
 
            if (!compression) {
                /* Add padding to make sure we have n mod 4 == 0 bytes per row */
                for (xpos = padding; xpos > 0; --xpos) {
                    Putchar('\0', out);
                }
            } else {
                int compressed_size = 0;
                uncompressed_row = uncompressed_row_start;
                if ((compressed_size = compress_row(uncompressed_row, gdImageSX(im))) < 0) {
                    error = 1;
                    break;
                }
                bitmap_size += compressed_size;
 
 
                gdPutBuf(uncompressed_row, compressed_size, out);
                Putchar(BMP_RLE_COMMAND, out);
                Putchar(BMP_RLE_ENDOFLINE, out);
                bitmap_size += 2;
            }
        }
 
        if (compression && uncompressed_row) {
            gdFree(uncompressed_row);
            if (error != 0) {
                goto cleanup;
            }
            /* Update filesize based on new values and set compression flag */
            Putchar(BMP_RLE_COMMAND, out);
            Putchar(BMP_RLE_ENDOFBITMAP, out);
            bitmap_size += 2;
 
            /* Write new total bitmap size */
            gdSeek(out, 2);
            gdBMPPutInt(out, total_size + bitmap_size);
 
            /* Total length of image data */
            gdSeek(out, 34);
            gdBMPPutInt(out, bitmap_size);
        }
 
    } else {
        for (row = (im->sy - 1); row >= 0; row--) {
            for (xpos = 0; xpos < im->sx; xpos++) {
                pixel = gdImageGetPixel(im, xpos, row);
 
                Putchar(gdTrueColorGetBlue(pixel), out);
                Putchar(gdTrueColorGetGreen(pixel), out);
                Putchar(gdTrueColorGetRed(pixel), out);
            }
 
            /* Add padding to make sure we have n mod 4 == 0 bytes per row */
            for (xpos = padding; xpos > 0; --xpos) {
                Putchar('\0', out);
            }
        }
    }
 
 
    /* If we needed a tmpfile for compression copy it over to out_original */
    if (tmpfile_for_compression) {
        unsigned char* copy_buffer = NULL;
        int buffer_size = 0;
 
        gdSeek(out, 0);
        copy_buffer = (unsigned char *) gdMalloc(1024 * sizeof(unsigned char));
        if (copy_buffer == NULL) {
            goto cleanup;
        }
 
        while ((buffer_size = gdGetBuf(copy_buffer, 1024, out)) != EOF) {
            if (buffer_size == 0) {
                break;
            }
            gdPutBuf(copy_buffer , buffer_size, out_original);
        }
        gdFree(copy_buffer);
 
        /* Replace the temp with the original which now has data */
        out->gd_free(out);
        out = out_original;
        out_original = NULL;
    }
 
cleanup:
    if (tmpfile_for_compression) {
#ifdef _WIN32
        _rmtmp();
#else
        fclose(tmpfile_for_compression);
#endif
        tmpfile_for_compression = NULL;
    }
 
    if (out_original) {
        out_original->gd_free(out_original);
    }
    return;
}
 
static int compress_row(unsigned char *row, int length)
{
    int rle_type = 0;
    int compressed_length = 0;
    int pixel = 0, compressed_run = 0, rle_compression = 0;
    unsigned char *uncompressed_row = NULL, *uncompressed_rowp = NULL, *uncompressed_start = NULL;
 
    uncompressed_row = (unsigned char *) gdMalloc(length);
    if (!uncompressed_row) {
        return -1;
    }
 
    memcpy(uncompressed_row, row, length);
    uncompressed_start = uncompressed_rowp = uncompressed_row;
 
    for (pixel = 0; pixel < length; pixel++) {
        if (compressed_run == 0) {
            uncompressed_row = uncompressed_rowp;
            compressed_run++;
            uncompressed_rowp++;
            rle_type = BMP_RLE_TYPE_RAW;
            continue;
        }
 
        if (compressed_run == 1) {
            /* Compare next byte */
            if (memcmp(uncompressed_rowp, uncompressed_rowp - 1, 1) == 0) {
                rle_type = BMP_RLE_TYPE_RLE;
            }
        }
 
        if (rle_type == BMP_RLE_TYPE_RLE) {
            if (compressed_run >= 128 || memcmp(uncompressed_rowp, uncompressed_rowp - 1, 1) != 0) {
                /* more than what we can store in a single run or run is over due to non match, force write */
                rle_compression = build_rle_packet(row, rle_type, compressed_run, uncompressed_row);
                row += rle_compression;
                compressed_length += rle_compression;
                compressed_run = 0;
                pixel--;
            } else {
                compressed_run++;
                uncompressed_rowp++;
            }
        } else {
            if (compressed_run >= 128 || memcmp(uncompressed_rowp, uncompressed_rowp - 1, 1) == 0) {
                /* more than what we can store in a single run or run is over due to match, force write */
                rle_compression = build_rle_packet(row, rle_type, compressed_run, uncompressed_row);
                row += rle_compression;
                compressed_length += rle_compression;
                compressed_run = 0;
                pixel--;
            } else {
                /* add this pixel to the row */
                compressed_run++;
                uncompressed_rowp++;
            }
 
        }
    }
 
    if (compressed_run) {
        compressed_length += build_rle_packet(row, rle_type, compressed_run, uncompressed_row);
    }
 
    gdFree(uncompressed_start);
 
    return compressed_length;
}
 
static int build_rle_packet(unsigned char *row, int packet_type, int length, unsigned char *data)
{
    int compressed_size = 0;
    if (length < 1 || length > 128) {
        return 0;
    }
 
    /* Bitmap specific cases is that we can't have uncompressed rows of length 1 or 2 */
    if (packet_type == BMP_RLE_TYPE_RAW && length < 3) {
        int i = 0;
        for (i = 0; i < length; i++) {
            compressed_size += 2;
            memset(row, 1, 1);
            row++;
 
            memcpy(row, data++, 1);
            row++;
        }
    } else if (packet_type == BMP_RLE_TYPE_RLE) {
        compressed_size = 2;
        memset(row, length, 1);
        row++;
 
        memcpy(row, data, 1);
        row++;
    } else {
        compressed_size = 2 + length;
        memset(row, BMP_RLE_COMMAND, 1);
        row++;
 
        memset(row, length, 1);
        row++;
 
        memcpy(row, data, length);
        row += length;
 
        /* Must be an even number for an uncompressed run */
        if (length % 2) {
            memset(row, 0, 1);
            row++;
            compressed_size++;
        }
    }
    return compressed_size;
}
 
/*
    Function: gdImageCreateFromBmp
*/
gdImagePtr gdImageCreateFromBmp(FILE * inFile)
{
    gdImagePtr im = 0;
    gdIOCtx *in = gdNewFileCtx(inFile);
    if (in == NULL) return NULL;
    im = gdImageCreateFromBmpCtx(in);
    in->gd_free(in);
    return im;
}
 
/*
    Function: gdImageCreateFromBmpPtr
*/
gdImagePtr gdImageCreateFromBmpPtr(int size, void *data)
{
    gdImagePtr im;
    gdIOCtx *in = gdNewDynamicCtxEx(size, data, 0);
    if (in == NULL) return NULL;
    im = gdImageCreateFromBmpCtx(in);
    in->gd_free(in);
    return im;
}
 
/*
    Function: gdImageCreateFromBmpCtx
*/
gdImagePtr gdImageCreateFromBmpCtx(gdIOCtxPtr infile)
{
    bmp_hdr_t *hdr;
    bmp_info_t *info;
    gdImagePtr im = NULL;
    int error = 0;
 
    if (!(hdr= (bmp_hdr_t *)gdCalloc(1, sizeof(bmp_hdr_t)))) {
        return NULL;
    }
 
    if (bmp_read_header(infile, hdr)) {
        gdFree(hdr);
        return NULL;
    }
 
    if (hdr->magic != 0x4d42) {
        gdFree(hdr);
        return NULL;
    }
 
    if (!(info = (bmp_info_t *)gdCalloc(1, sizeof(bmp_info_t)))) {
        gdFree(hdr);
        return NULL;
    }
 
    if (bmp_read_info(infile, info)) {
        gdFree(hdr);
        gdFree(info);
        return NULL;
    }
 
    BMP_DEBUG(printf("Numcolours: %d\n", info->numcolors));
    BMP_DEBUG(printf("Width: %d\n", info->width));
    BMP_DEBUG(printf("Height: %d\n", info->height));
    BMP_DEBUG(printf("Planes: %d\n", info->numplanes));
    BMP_DEBUG(printf("Depth: %d\n", info->depth));
    BMP_DEBUG(printf("Offset: %d\n", hdr->off));
 
    if (info->depth >= 16) {
        im = gdImageCreateTrueColor(info->width, info->height);
    } else {
        im = gdImageCreate(info->width, info->height);
    }
 
    if (!im) {
        gdFree(hdr);
        gdFree(info);
        return NULL;
    }
 
    switch (info->depth) {
    case 1:
        BMP_DEBUG(printf("1-bit image\n"));
        error = bmp_read_1bit(im, infile, info, hdr);
        break;
    case 4:
        BMP_DEBUG(printf("4-bit image\n"));
        error = bmp_read_4bit(im, infile, info, hdr);
        break;
    case 8:
        BMP_DEBUG(printf("8-bit image\n"));
        error = bmp_read_8bit(im, infile, info, hdr);
        break;
    case 16:
    case 24:
    case 32:
        BMP_DEBUG(printf("Direct BMP image\n"));
        error = bmp_read_direct(im, infile, info, hdr);
        break;
    default:
        BMP_DEBUG(printf("Unknown bit count\n"));
        error = 1;
    }
 
    gdFree(hdr);
    gdFree(info);
 
    if (error) {
        gdImageDestroy(im);
        return NULL;
    }
 
    return im;
}
 
static int bmp_read_header(gdIOCtx *infile, bmp_hdr_t *hdr)
{
    if(
        !gdGetWordLSB(&hdr->magic, infile) ||
        !gdGetIntLSB(&hdr->size, infile) ||
        !gdGetWordLSB(&hdr->reserved1, infile) ||
        !gdGetWordLSB(&hdr->reserved2 , infile) ||
        !gdGetIntLSB(&hdr->off , infile)
    ) {
        return 1;
    }
    return 0;
}
 
static int bmp_read_info(gdIOCtx *infile, bmp_info_t *info)
{
    /* read BMP length so we can work out the version */
    if (!gdGetIntLSB(&info->len, infile)) {
        return 1;
    }
 
    switch (info->len) {
        /* For now treat Windows v4 + v5 as v3 */
    case BMP_WINDOWS_V3:
    case BMP_WINDOWS_V4:
    case BMP_WINDOWS_V5:
        BMP_DEBUG(printf("Reading Windows Header\n"));
        if (bmp_read_windows_v3_info(infile, info)) {
            return 1;
        }
        break;
    case BMP_OS2_V1:
        if (bmp_read_os2_v1_info(infile, info)) {
            return 1;
        }
        break;
    case BMP_OS2_V2:
        if (bmp_read_os2_v2_info(infile, info)) {
            return 1;
        }
        break;
    default:
        BMP_DEBUG(printf("Unhandled bitmap\n"));
        return 1;
    }
    return 0;
}
 
static int bmp_read_windows_v3_info(gdIOCtxPtr infile, bmp_info_t *info)
{
    if (
        !gdGetIntLSB(&info->width, infile) ||
        !gdGetIntLSB(&info->height, infile) ||
        !gdGetWordLSB(&info->numplanes, infile) ||
        !gdGetWordLSB(&info->depth, infile) ||
        !gdGetIntLSB(&info->enctype, infile) ||
        !gdGetIntLSB(&info->size, infile) ||
        !gdGetIntLSB(&info->hres, infile) ||
        !gdGetIntLSB(&info->vres, infile) ||
        !gdGetIntLSB(&info->numcolors, infile) ||
        !gdGetIntLSB(&info->mincolors, infile)
    ) {
        return 1;
    }
 
    if (info->height < 0) {
        info->topdown = 1;
        info->height = -info->height;
    } else {
        info->topdown = 0;
    }
 
    info->type = BMP_PALETTE_4;
 
    if (info->width <= 0 || info->height <= 0 || info->numplanes <= 0 ||
            info->depth <= 0  || info->numcolors < 0 || info->mincolors < 0) {
        return 1;
    }
 
    return 0;
}
 
static int bmp_read_os2_v1_info(gdIOCtxPtr infile, bmp_info_t *info)
{
    if (
        !gdGetWordLSB((signed short int *)&info->width, infile) ||
        !gdGetWordLSB((signed short int *)&info->height, infile) ||
        !gdGetWordLSB(&info->numplanes, infile) ||
        !gdGetWordLSB(&info->depth, infile)
    ) {
        return 1;
    }
 
    /* OS2 v1 doesn't support topdown */
    info->topdown = 0;
 
    info->numcolors = 1 << info->depth;
    info->type = BMP_PALETTE_3;
 
    if (info->width <= 0 || info->height <= 0 || info->numplanes <= 0 ||
            info->depth <= 0 || info->numcolors < 0) {
        return 1;
    }
 
    return 0;
}
 
static int bmp_read_os2_v2_info(gdIOCtxPtr infile, bmp_info_t *info)
{
    char useless_bytes[24];
    if (
        !gdGetIntLSB(&info->width, infile) ||
        !gdGetIntLSB(&info->height, infile) ||
        !gdGetWordLSB(&info->numplanes, infile) ||
        !gdGetWordLSB(&info->depth, infile) ||
        !gdGetIntLSB(&info->enctype, infile) ||
        !gdGetIntLSB(&info->size, infile) ||
        !gdGetIntLSB(&info->hres, infile) ||
        !gdGetIntLSB(&info->vres, infile) ||
        !gdGetIntLSB(&info->numcolors, infile) ||
        !gdGetIntLSB(&info->mincolors, infile)
    ) {
        return 1;
    }
 
    /* Let's seek the next 24 pointless bytes, we don't care too much about it */
    if (!gdGetBuf(useless_bytes, 24, infile)) {
        return 1;
    }
 
    if (info->height < 0) {
        info->topdown = 1;
        info->height = -info->height;
    } else {
        info->topdown = 0;
    }
 
    info->type = BMP_PALETTE_4;
 
    if (info->width <= 0 || info->height <= 0 || info->numplanes <= 0 ||
            info->depth <= 0  || info->numcolors < 0 || info->mincolors < 0) {
        return 1;
    }
 
 
    return 0;
}
 
static int bmp_read_direct(gdImagePtr im, gdIOCtxPtr infile, bmp_info_t *info, bmp_hdr_t *header)
{
    int ypos = 0, xpos = 0, row = 0;
    int padding = 0, alpha = 0, red = 0, green = 0, blue = 0;
    signed short int data = 0;
 
    switch(info->enctype) {
    case BMP_BI_RGB:
        /* no-op */
        break;
 
    case BMP_BI_BITFIELDS:
        if (info->depth == 24) {
            BMP_DEBUG(printf("Bitfield compression isn't supported for 24-bit\n"));
            return 1;
        }
        BMP_DEBUG(printf("Currently no bitfield support\n"));
        return 1;
        break;
 
    case BMP_BI_RLE8:
        if (info->depth != 8) {
            BMP_DEBUG(printf("RLE is only valid for 8-bit images\n"));
            return 1;
        }
        break;
    case BMP_BI_RLE4:
        if (info->depth != 4) {
            BMP_DEBUG(printf("RLE is only valid for 4-bit images\n"));
            return 1;
        }
        break;
    case BMP_BI_JPEG:
    case BMP_BI_PNG:
    default:
        BMP_DEBUG(printf("Unsupported BMP compression format\n"));
        return 1;
    }
 
    /* There is a chance the data isn't until later, would be weird but it is possible */
    if (gdTell(infile) != header->off) {
        /* Should make sure we don't seek past the file size */
        if (!gdSeek(infile, header->off)) {
            return 1;
        }
    }
 
    /* The line must be divisible by 4, else it's padded with NULLs */
    padding = ((int)(info->depth / 8) * info->width) % 4;
    if (padding) {
        padding = 4 - padding;
    }
 
 
    for (ypos = 0; ypos < info->height; ++ypos) {
        if (info->topdown) {
            row = ypos;
        } else {
            row = info->height - ypos - 1;
        }
 
        for (xpos = 0; xpos < info->width; xpos++) {
            if (info->depth == 16) {
                if (!gdGetWordLSB(&data, infile)) {
                    return 1;
                }
                BMP_DEBUG(printf("Data: %X\n", data));
                red = ((data & 0x7C00) >> 10) << 3;
                green = ((data & 0x3E0) >> 5) << 3;
                blue = (data & 0x1F) << 3;
                BMP_DEBUG(printf("R: %d, G: %d, B: %d\n", red, green, blue));
            } else if (info->depth == 24) {
                if (!gdGetByte(&blue, infile) || !gdGetByte(&green, infile) || !gdGetByte(&red, infile)) {
                    return 1;
                }
            } else {
                if (!gdGetByte(&blue, infile) || !gdGetByte(&green, infile) || !gdGetByte(&red, infile) || !gdGetByte(&alpha, infile)) {
                    return 1;
                }
            }
            /*alpha = gdAlphaMax - (alpha >> 1);*/
            gdImageSetPixel(im, xpos, row, gdTrueColor(red, green, blue));
        }
        for (xpos = padding; xpos > 0; --xpos) {
            if (!gdGetByte(&red, infile)) {
                return 1;
            }
        }
    }
 
    return 0;
}
 
static int bmp_read_palette(gdImagePtr im, gdIOCtxPtr infile, int count, int read_four)
{
    int i;
    int r, g, b, z;
 
    for (i = 0; i < count; i++) {
        if (
            !gdGetByte(&b, infile) ||
            !gdGetByte(&g, infile) ||
            !gdGetByte(&r, infile) ||
            (read_four && !gdGetByte(&z, infile))
        ) {
            return 1;
        }
        im->red[i] = r;
        im->green[i] = g;
        im->blue[i] = b;
        im->open[i] = 1;
    }
    return 0;
}
 
static int bmp_read_1bit(gdImagePtr im, gdIOCtxPtr infile, bmp_info_t *info, bmp_hdr_t *header)
{
    int ypos = 0, xpos = 0, row = 0, index = 0;
    int padding = 0, current_byte = 0, bit = 0;
 
    if (info->enctype != BMP_BI_RGB) {
        return 1;
    }
 
    if (!info->numcolors) {
        info->numcolors = 2;
    } else if (info->numcolors < 0 || info->numcolors > 2) {
        return 1;
    }
 
    if (bmp_read_palette(im, infile, info->numcolors, (info->type == BMP_PALETTE_4))) {
        return 1;
    }
 
    im->colorsTotal = info->numcolors;
 
    /* There is a chance the data isn't until later, would be weird but it is possible */
    if (gdTell(infile) != header->off) {
        /* Should make sure we don't seek past the file size */
        if (!gdSeek(infile, header->off)) {
            return 1;
        }
    }
 
    /* The line must be aligned on a 32 bits word, else it is padded with zeros */
    padding = (info->width + 7) / 8 % 4;
    if (padding) {
        padding = 4 - padding;
    }
 
    for (ypos = 0; ypos < info->height; ++ypos) {
        if (info->topdown) {
            row = ypos;
        } else {
            row = info->height - ypos - 1;
        }
 
        for (xpos = 0; xpos < info->width; xpos += 8) {
            /* Bitmaps are always aligned in bytes so we'll never overflow */
            if (!gdGetByte(&current_byte, infile)) {
                return 1;
            }
 
            for (bit = 0; bit < 8; bit++) {
                index = ((current_byte & (0x80 >> bit)) != 0 ? 0x01 : 0x00);
                if (im->open[index]) {
                    im->open[index] = 0;
                }
                gdImageSetPixel(im, xpos + bit, row, index);
                /* No need to read anything extra */
                if ((xpos + bit) >= info->width) {
                    break;
                }
            }
        }
 
        for (xpos = padding; xpos > 0; --xpos) {
            if (!gdGetByte(&index, infile)) {
                return 1;
            }
        }
    }
    return 0;
}
 
static int bmp_read_4bit(gdImagePtr im, gdIOCtxPtr infile, bmp_info_t *info, bmp_hdr_t *header)
{
    int ypos = 0, xpos = 0, row = 0, index = 0;
    int padding = 0, current_byte = 0;
 
    if (info->enctype != BMP_BI_RGB && info->enctype != BMP_BI_RLE4) {
        return 1;
    }
 
    if (!info->numcolors) {
        info->numcolors = 16;
    } else if (info->numcolors < 0 || info->numcolors > 16) {
        return 1;
    }
 
    if (bmp_read_palette(im, infile, info->numcolors, (info->type == BMP_PALETTE_4))) {
        return 1;
    }
 
    im->colorsTotal = info->numcolors;
 
    /* There is a chance the data isn't until later, would be weird but it is possible */
    if (gdTell(infile) != header->off) {
        /* Should make sure we don't seek past the file size */
        if (!gdSeek(infile, header->off)) {
            return 1;
        }
    }
 
    /* The line must be divisible by 4, else it's padded with NULLs */
    padding = ((int)ceil(0.5 * info->width)) % 4;
    if (padding) {
        padding = 4 - padding;
    }
 
    switch (info->enctype) {
    case BMP_BI_RGB:
        for (ypos = 0; ypos < info->height; ++ypos) {
            if (info->topdown) {
                row = ypos;
            } else {
                row = info->height - ypos - 1;
            }
 
            for (xpos = 0; xpos < info->width; xpos += 2) {
                if (!gdGetByte(&current_byte, infile)) {
                    return 1;
                }
 
                index = (current_byte >> 4) & 0x0f;
                if (im->open[index]) {
                    im->open[index] = 0;
                }
                gdImageSetPixel(im, xpos, row, index);
 
                /* This condition may get called often, potential optimsations */
                if (xpos >= info->width) {
                    break;
                }
 
                index = current_byte & 0x0f;
                if (im->open[index]) {
                    im->open[index] = 0;
                }
                gdImageSetPixel(im, xpos + 1, row, index);
            }
 
            for (xpos = padding; xpos > 0; --xpos) {
                if (!gdGetByte(&index, infile)) {
                    return 1;
                }
            }
        }
        break;
 
    case BMP_BI_RLE4:
        if (bmp_read_rle(im, infile, info)) {
            return 1;
        }
        break;
 
    default:
        return 1;
    }
    return 0;
}
 
static int bmp_read_8bit(gdImagePtr im, gdIOCtxPtr infile, bmp_info_t *info, bmp_hdr_t *header)
{
    int ypos = 0, xpos = 0, row = 0, index = 0;
    int padding = 0;
 
    if (info->enctype != BMP_BI_RGB && info->enctype != BMP_BI_RLE8) {
        return 1;
    }
 
    if (!info->numcolors) {
        info->numcolors = 256;
    } else if (info->numcolors < 0 || info->numcolors > 256) {
        return 1;
    }
 
    if (bmp_read_palette(im, infile, info->numcolors, (info->type == BMP_PALETTE_4))) {
        return 1;
    }
 
    im->colorsTotal = info->numcolors;
 
    /* There is a chance the data isn't until later, would be weird but it is possible */
    if (gdTell(infile) != header->off) {
        /* Should make sure we don't seek past the file size */
        if (!gdSeek(infile, header->off)) {
            return 1;
        }
    }
 
    /* The line must be divisible by 4, else it's padded with NULLs */
    padding = (1 * info->width) % 4;
    if (padding) {
        padding = 4 - padding;
    }
 
    switch (info->enctype) {
    case BMP_BI_RGB:
        for (ypos = 0; ypos < info->height; ++ypos) {
            if (info->topdown) {
                row = ypos;
            } else {
                row = info->height - ypos - 1;
            }
 
            for (xpos = 0; xpos < info->width; ++xpos) {
                if (!gdGetByte(&index, infile)) {
                    return 1;
                }
 
                if (im->open[index]) {
                    im->open[index] = 0;
                }
                gdImageSetPixel(im, xpos, row, index);
            }
            /* Could create a new variable, but it isn't really worth it */
            for (xpos = padding; xpos > 0; --xpos) {
                if (!gdGetByte(&index, infile)) {
                    return 1;
                }
            }
        }
        break;
 
    case BMP_BI_RLE8:
        if (bmp_read_rle(im, infile, info)) {
            return 1;
        }
        break;
 
    default:
        return 1;
    }
    return 0;
}
 
static int bmp_read_rle(gdImagePtr im, gdIOCtxPtr infile, bmp_info_t *info)
{
    int ypos = 0, xpos = 0, row = 0, index = 0;
    int rle_length = 0, rle_data = 0;
    int padding = 0;
    int i = 0, j = 0;
    int pixels_per_byte = 8 / info->depth;
 
    for (ypos = 0; ypos < info->height && xpos <= info->width;) {
        if (!gdGetByte(&rle_length, infile) || !gdGetByte(&rle_data, infile)) {
            return 1;
        }
        row = info->height - ypos - 1;
 
        if (rle_length != BMP_RLE_COMMAND) {
            if (im->open[rle_data]) {
                im->open[rle_data] = 0;
            }
 
            for (i = 0; (i < rle_length) && (xpos < info->width);) {
                for (j = 1; (j <= pixels_per_byte) && (xpos < info->width) && (i < rle_length); j++, xpos++, i++) {
                    index = (rle_data & (((1 << info->depth) - 1) << (8 - (j * info->depth)))) >> (8 - (j * info->depth));
                    if (im->open[index]) {
                        im->open[index] = 0;
                    }
                    gdImageSetPixel(im, xpos, row, index);
                }
            }
        } else if (rle_length == BMP_RLE_COMMAND && rle_data > 2) {
            /* Uncompressed RLE needs to be even */
            padding = 0;
            for (i = 0; (i < rle_data) && (xpos < info->width); i += pixels_per_byte) {
                int max_pixels = pixels_per_byte;
 
                if (!gdGetByte(&index, infile)) {
                    return 1;
                }
                padding++;
 
                if (rle_data - i < max_pixels) {
                    max_pixels = rle_data - i;
                }
 
                for (j = 1; (j <= max_pixels)  && (xpos < info->width); j++, xpos++) {
                    int temp = (index >> (8 - (j * info->depth))) & ((1 << info->depth) - 1);
                    if (im->open[temp]) {
                        im->open[temp] = 0;
                    }
                    gdImageSetPixel(im, xpos, row, temp);
                }
            }
 
            /* Make sure the bytes read are even */
            if (padding % 2 && !gdGetByte(&index, infile)) {
                return 1;
            }
        } else if (rle_length == BMP_RLE_COMMAND && rle_data == BMP_RLE_ENDOFLINE) {
            /* Next Line */
            xpos = 0;
            ypos++;
        } else if (rle_length == BMP_RLE_COMMAND && rle_data == BMP_RLE_DELTA) {
            /* Delta Record, used for bmp files that contain other data*/
            if (!gdGetByte(&rle_length, infile) || !gdGetByte(&rle_data, infile)) {
                return 1;
            }
            xpos += rle_length;
            ypos += rle_data;
        } else if (rle_length == BMP_RLE_COMMAND && rle_data == BMP_RLE_ENDOFBITMAP) {
            /* End of bitmap */
            break;
        }
    }
    return 0;
}