I need to implement a Box Blur algorithm for a school project and I found this algorithm online. My issue is that i can't open the "result.bmp" file after the algorithm is done. It says the file is either corrupted or damaged and I can't seem to find the cause of this issue.
Code:
FILE* fIn = fopen("test.bmp", "r"); // Input File name
FILE* fOut = fopen("result.bmp", "w "); // Output File name
int i, j, y, x;
unsigned char byte[54];
for (i = 0; i < 54; i ) // read the 54 byte header from fIn
{
byte[i] = fgetc(fIn);
}
fwrite(byte, sizeof(unsigned char), 54, fOut); // write the header back
// extract image height, width and bitDepth from imageHeader
int height = *(int*)&byte[18];
int width = *(int*)&byte[22];
int bitDepth = *(int*)&byte[28];
printf("width: %d\n", width);
printf("height: %d\n", height);
int size = height * width;
unsigned char** buffer = (unsigned char**)malloc(size * sizeof(unsigned char*));
for (int i = 0; i < size; i )
buffer[i] = (unsigned char*)malloc(3 * sizeof(unsigned char));
unsigned char** out = (unsigned char**)malloc(size * sizeof(unsigned char*));
for (int i = 0; i < size; i )
out[i] = (unsigned char*)malloc(3 * sizeof(unsigned char));
for (i = 0; i < size; i )
{
buffer[i][2] = getc(fIn); // blue
buffer[i][1] = getc(fIn); // green
buffer[i][0] = getc(fIn); // red
}
float v = 1.0 / 9.0; // initialize the blurring kernel
float kernel[3][3] = { {v,v,v},
{v,v,v},
{v,v,v} };
for (x = 1; x < height - 1; x )
{
for (y = 1; y < width - 1; y )
{
float sum0 = 0.0;
float sum1 = 0.0;
float sum2 = 0.0;
for (i = -1; i <= 1; i )
{
for (j = -1; j <= 1; j )
{
// matrix multiplication with kernel with every color plane
sum0 = sum0 (float)kernel[i 1][j 1] * buffer[(x i) * width (y j)][0];
sum1 = sum1 (float)kernel[i 1][j 1] * buffer[(x i) * width (y j)][1];
sum2 = sum2 (float)kernel[i 1][j 1] * buffer[(x i) * width (y j)][2];
}
}
out[(x)*width (y)][0] = (unsigned char)sum0;
out[(x)*width (y)][1] = (unsigned char)sum1;
out[(x)*width (y)][2] = (unsigned char)sum2;
}
}
for (i = 0; i < size; i ) //write image data back to the file
{
fputc(out[i][2], fOut);
fputc(out[i][1], fOut);
fputc(out[i][0], fOut);
}
The algorithm successfully reads the width and the height of the input image, it creates the output file but the file cannot be opened.
CodePudding user response：
Your code is very close but has some issues:
- You can calculate the byte count per line considering the 4-byte alignment
with
((width * 3 3) / 4) * 4. - The addesses of
widthandheightare vice versa. - You should not cast the return value of
malloc(). - Bmp file header is composed of
BMP File header(14 bytes fixed) andDIB header(variable size). As the size of DIB header is stored in the starting 4 bytes of the DIB header, lets read the 18 bytes (= 14 4) at first, determine the remaining header size, then read the rest of DIB header.
Then the modified version will look like:
#include <stdio.h>
#include <stdlib.h>
#define INFILE "test.bmp" // input file name
#define OUTFILE "result.bmp" // output file name
#define HEADER1 (14 4) // Bitmap File Header word for header size
#define HEADER2 (124 - 4) // DIB (Information) File Header - word for header size
int main()
{
FILE *fIn = fopen(INFILE, "r");
if (fIn == NULL) {
perror(INFILE);
exit(1);
}
FILE *fOut = fopen(OUTFILE, "w ");
if (fOut == NULL) {
perror(OUTFILE);
exit(1);
}
int i, j, y, x;
int dibsize; // size of DIB Header
unsigned char header1[HEADER1];
unsigned char header2[HEADER2];
fread(header1, sizeof(unsigned char), HEADER1, fIn); // read file header DIB header size
dibsize = *(int *)&header1[14]; // size of DIB header
fwrite(header1, sizeof(unsigned char), HEADER1, fOut); // write the header back
fread(header2, sizeof(unsigned char), dibsize - 4, fIn); // read remaining DIB header except for the word for the header size
fwrite(header2, sizeof(unsigned char), dibsize - 4, fOut); // write the header back
// extract image height, width and bitDepth from imageHeader
int width = *(int *)&header2[0];
int height = *(int *)&header2[4];
int bitDepth = *(int *)&header2[20];
int bytesperline = ((width * 3 3) / 4) * 4; // bytes per line including 4-byte alignment
printf("width: %d\n", width);
printf("height: %d\n", height);
// printf("bytesperline: %d\n", bytesperline);
int size = height * width;
unsigned char **buffer = malloc(size * sizeof(unsigned char *));
for (int i = 0; i < size; i )
buffer[i] = malloc(3 * sizeof(unsigned char));
unsigned char **out = malloc(size * sizeof(unsigned char *));
for (int i = 0; i < size; i )
out[i] = malloc(3 * sizeof(unsigned char));
for (i = 0; i < height; i )
{
for (j = 0; j < width; j )
{
buffer[i * width j][2] = getc(fIn); // blue
buffer[i * width j][1] = getc(fIn); // green
buffer[i * width j][0] = getc(fIn); // red
}
for (j = width * 3; j < bytesperline; j ) // zero padding for 4-byte alignment
{
getc(fIn);
}
}
float v = 1.0 / 9.0; // initialize the blurring kernel
float kernel[3][3] = { {v,v,v},
{v,v,v},
{v,v,v} };
for (x = 1; x < height - 1; x )
{
for (y = 1; y < width - 1; y )
{
float sum0 = 0.0;
float sum1 = 0.0;
float sum2 = 0.0;
for (i = -1; i <= 1; i )
{
for (j = -1; j <= 1; j )
{
// matrix multiplication with kernel with every color plane
sum0 = sum0 (float)kernel[i 1][j 1] * buffer[(x i) * width (y j)][0];
sum1 = sum1 (float)kernel[i 1][j 1] * buffer[(x i) * width (y j)][1];
sum2 = sum2 (float)kernel[i 1][j 1] * buffer[(x i) * width (y j)][2];
}
}
out[x * width y][0] = (unsigned char)sum0;
out[x * width y][1] = (unsigned char)sum1;
out[x * width y][2] = (unsigned char)sum2;
}
}
for (i = 0; i < height; i ) // write image data back to the file
{
for (j = 0; j < width; j )
{
fputc(out[i * width j][2], fOut); // blue
fputc(out[i * width j][1], fOut); // green
fputc(out[i * width j][0], fOut); // red
}
for (j = width * 3; j < bytesperline; j ) // zero padding for 4-byte alignment
{
fputc(0, fOut);
}
}
fclose(fIn);
fclose(fOut);
return 0;
}