Problem reading 8 bit greyscale images !
Hi everyone
I am trying to read and print the negative of a 8 bit gray scale .bmp image with the following code, unfortunately it reads only 2 of the .bmp images i have, but doesn't read the other .bmp images including the one i have attached lena256.bmp, even though its an 8 bit greyscale .bmp image.
All of them happen to have the same properties but with this code am unable to read all the .bmp files, only 2 wud give proper output :
Code:
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
/*-------STRUCTURES---------*/
typedef struct {int rows; int cols; int bits; unsigned char* data;} sImage;
/*-------PROTOTYPES---------*/
long getImageInfo(FILE*, long, int);
void copyImageInfo(FILE*, FILE*);
void copyColorTable(FILE*, FILE*, int);
int main()
{
FILE *bmpInput, *bmpOutput;
sImage originalImage;
unsigned char someChar;
unsigned char* pChar;
int nColors; /* BMP number of colors */
long fileSize; /* BMP file size */
int vectorSize; /* BMP vector size */
int r, c; /* r = rows, c = cols */
int pixels[600][600];
char imagein[30];
char imageout[30];
/* initialize pointer */
someChar = '0';
pChar = &someChar;
printf("Enter input image : ");
gets(imagein);
printf("Enter output image : ");
gets(imageout);
/*--------READ INPUT FILE------------*/
bmpInput = fopen(imagein, "rb");
fseek(bmpInput, 0L, SEEK_END);
/*--------DECLARE OUTPUT FILE--------*/
bmpOutput = fopen(imageout, "wb");
/*--------GET BMP DATA---------------*/
originalImage.cols = (int)getImageInfo(bmpInput, 18, 4);
originalImage.rows = (int)getImageInfo(bmpInput, 22, 4);
originalImage.bits = (int)getImageInfo(bmpInput, 28, 4);
fileSize = getImageInfo(bmpInput, 2, 4);
nColors = getImageInfo(bmpInput, 46, 4);
vectorSize = fileSize - (14 + 40 + 4*nColors);
/*-------PRINT DATA TO SCREEN-------------*/
printf("Width: %d\n", originalImage.cols);
printf("Height: %d\n", originalImage.rows);
printf("Bits per Pixel: %d\n", originalImage.bits);
printf("File size: %ld\n", fileSize);
printf("# Colors: %d\n", nColors);
printf("Vector size: %d\n", vectorSize);
copyImageInfo(bmpInput, bmpOutput);
copyColorTable(bmpInput, bmpOutput, nColors);
/*----START AT BEGINNING OF RASTER DATA-----*/
fseek(bmpInput, (54 + 4*nColors), SEEK_SET);
/*----------READ RASTER DATA----------*/
for(r=0; r<=originalImage.rows - 1; r++)
{
for(c=0; c<=originalImage.cols - 1; c++)
{
/*-----read data, reflect and write to output file----*/
fread(pChar, sizeof(char), 1, bmpInput);
pixels[r][c] = *pChar;
*pChar = 255 - *pChar;
fwrite(pChar, sizeof(char), 1, bmpOutput);
}
}
fclose(bmpInput);
fclose(bmpOutput);
getch();
}
/*----------GET IMAGE INFO SUBPROGRAM--------------*/
long getImageInfo(FILE* inputFile, long offset, int numberOfChars)
{
unsigned char *ptrC;
long value = 0L;
unsigned char dummy;
int i;
dummy = '0';
ptrC = &dummy;
fseek(inputFile, offset, SEEK_SET);
for(i=1; i<=numberOfChars; i++)
{
fread(ptrC, sizeof(char), 1, inputFile);
/* calculate value based on adding bytes */
value = (long)(value + (*ptrC)*(pow(256, (i-1))));
}
return(value);
} /* end of getImageInfo */
/*-------------COPIES HEADER AND INFO HEADER----------------*/
void copyImageInfo(FILE* inputFile, FILE* outputFile)
{
unsigned char *ptrC;
unsigned char dummy;
int i;
dummy = '0';
ptrC = &dummy;
fseek(inputFile, 0L, SEEK_SET);
fseek(outputFile, 0L, SEEK_SET);
for(i=0; i<=50; i++)
{
fread(ptrC, sizeof(char), 1, inputFile);
fwrite(ptrC, sizeof(char), 1, outputFile);
}
}
/*----------------COPIES COLOR TABLE-----------------------------*/
void copyColorTable(FILE* inputFile, FILE* outputFile, int nColors)
{
unsigned char *ptrC;
unsigned char dummy;
int i;
dummy = '0';
ptrC = &dummy;
fseek(inputFile, 54L, SEEK_SET);
fseek(outputFile, 54L, SEEK_SET);
for(i=0; i<=(4*nColors); i++) /* there are (4*nColors) bytesin color table */
{
fread(ptrC, sizeof(char), 1, inputFile);
fwrite(ptrC, sizeof(char), 1, outputFile);
}
}
I would be really grateful if someone could go through this code and find out where am going wrong.
Thank you in advance.
Anna
problem reading 8 bit gray scale .bmp image
Hey, thanks for ur suggestion , but i tried moving the int pixels[600][600] array above main and still am not able to run my code for lena256.bmp :( .... By moving the array above main , i hope you mean that i should just declare it above main , right ?
Quote:
Originally Posted by
swoopy
> int pixels[600][600];
You're probably clobbering the program stack with this array. I would either move the array above main() or create the array dynamically using malloc. I tried your code, and once I moved the array above main(), it ran fine.
