Thread: 8Bit Grayscale Bitmap

Hello everyone,

I cannot seem to read in an 8bit grayscale image into an array. Here is my code.

Code:

#include <stdio.h>#include <stdlib.h>
#include <string.h>


struct BitMap
{
    short Type;
    long Size;
    short Reserve1;
    short Reserve2;
    long OffBits;
    long biSize;
    long biWidth;
    long biHeight;
    short biPlanes;
    short biBitCount;
    long biCompression;
    long biSizeImage;
    long biXPelsPerMeter;
    long biYPelsPerMeter;
    long biClrUsed;
    long biClrImportant;
}Header;


int main( void ){


    FILE *BMPFile = fopen ("MriHotrod.bmp", "rb");


    if(BMPFile == NULL){
        return;
    }


    unsigned char DataBuff[128][128];
    int i;
    int j;


    memset(&Header, 0, sizeof(Header));


    fread(&Header.Type, 2, 1, BMPFile);
    fread(&Header.Size, 4, 1, BMPFile);
    fread(&Header.Reserve1, 2, 1, BMPFile);
    fread(&Header.Reserve2, 2, 1, BMPFile);
    fread(&Header.OffBits, 4, 1, BMPFile);
    fread(&Header.biSize, 4, 1, BMPFile);
    fread(&Header.biWidth, 4, 1, BMPFile);
    fread(&Header.biHeight, 4, 1, BMPFile);
    fread(&Header.biPlanes, 2, 1, BMPFile);
    fread(&Header.biBitCount, 2, 1, BMPFile);
    fread(&Header.biCompression, 4, 1, BMPFile);
    fread(&Header.biSizeImage, 4, 1, BMPFile);
    fread(&Header.biXPelsPerMeter, 4, 1, BMPFile);
    fread(&Header.biYPelsPerMeter, 4, 1, BMPFile);
    fread(&Header.biClrUsed, 4, 1, BMPFile);
    fread(&Header.biClrImportant, 4, 1, BMPFile);


    printf("\nType:%hd\n", Header.Type);
    printf("Size:%ld\n", Header.Size);
    printf("Reserve1:%hd\n", Header.Reserve1);
    printf("Reserve2:%hd\n", Header.Reserve2);
    printf("OffBits:%ld\n", Header.OffBits);
    printf("biSize:%ld\n", Header.biSize);
    printf("Width:%ld\n", Header.biWidth);
    printf("Height:%ld\n", Header.biHeight);
    printf("biPlanes:%hd\n", Header.biPlanes);
    printf("biBitCount:%hd\n", Header.biBitCount);
    printf("biCompression:%ld\n", Header.biCompression);
    printf("biSizeImage:%ld\n", Header.biSizeImage);
    printf("biXPelsPerMeter:%ld\n", Header.biXPelsPerMeter);
    printf("biYPelsPerMeter:%ld\n", Header.biYPelsPerMeter);
    printf("biClrUsed:%ld\n", Header.biClrUsed);
    printf("biClrImportant:%ld\n\n", Header.biClrImportant);


    for(i=0; i<Header.biWidth; i++){            // Not right, but unsure how to fix
        for(j=0; j<Header.biHeight; j++){
            DataBuff[i][j] = getc(BMPFile);
            printf("%02d ",DataBuff[i][j]);
        }
    }


    fclose(BMPFile);


    return 0;
}

Header Output

Type:19778
Size:17462
Reserve1:0
Reserve2:0
OffBits:1078
biSize:40
Width:128
Height:128
biPlanes:1
biBitCount:8
biCompression:0
biSizeImage:0
biXPelsPerMeter:0
biYPelsPerMeter:0
biClrUsed:256
biClrImportant:0

Thanks,

Shinobii

You need to skip OffBits (1078) bytes from (I believe) the beginning of the file before reading the bitmap data. Also, keep in mind that the bitmap is stored "upside down", where the last row is stored first.