2 Attachment(s)
Resizing BMP Files [Solved]
Hey guys,
I'm currently studying a CS course, and I have a problem set I can't seem to solve, we're required to make a small program that takes 3 arguments: (factor, file.bmp, file2.bmp) and resizes the first bmp by factor then stores it in the second file.
I've supplied my code along with the output of a sample run in an attachment.
This is a header file supplied by our instructor
bmp.h
Code:
#include <stdint.h>
/**
* Common Data Types
*
* The data types in this section are essentially aliases for C/C++
* primitive data types.
*
* Adapted from http://msdn.microsoft.com/en-us/library/cc230309(PROT.10).aspx.
* See http://en.wikipedia.org/wiki/Stdint.h for more on stdint.h.
*/
typedef uint8_t BYTE;
typedef uint32_t DWORD;
typedef int32_t LONG;
typedef uint16_t WORD;
#define HEADER 54 // number of bytes offset for header
/**
* BITMAPFILEHEADER
*
* The BITMAPFILEHEADER structure contains information about the type, size,
* and layout of a file that contains a DIB [device-independent bitmap].
*
* Adapted from http://msdn.microsoft.com/en-us/library/dd183374(VS.85).aspx.
*/
typedef struct
{
WORD bfType;
DWORD bfSize;
WORD bfReserved1;
WORD bfReserved2;
DWORD bfOffBits;
} __attribute__((__packed__))
BITMAPFILEHEADER;
/**
* BITMAPINFOHEADER
*
* The BITMAPINFOHEADER structure contains information about the
* dimensions and color format of a DIB [device-independent bitmap].
*
* Adapted from http://msdn.microsoft.com/en-us/library/dd183376(VS.85).aspx.
*/
typedef struct
{
DWORD biSize;
LONG biWidth;
LONG biHeight;
WORD biPlanes;
WORD biBitCount;
DWORD biCompression;
DWORD biSizeImage;
LONG biXPelsPerMeter;
LONG biYPelsPerMeter;
DWORD biClrUsed;
DWORD biClrImportant;
} __attribute__((__packed__))
BITMAPINFOHEADER;
/**
* RGBTRIPLE
*
* This structure describes a color consisting of relative intensities of
* red, green, and blue.
*
* Adapted from http://msdn.microsoft.com/en-us/library/aa922590.aspx.
*/
typedef struct
{
BYTE rgbtBlue;
BYTE rgbtGreen;
BYTE rgbtRed;
} __attribute__((__packed__))
RGBTRIPLE;
Now here's my code resize.c
Code:
#include <stdio.h>
#include <stdlib.h>
#include "bmp.h"
int main(int argc, char* argv[])
{
// ensure proper usage
if (argc != 4)
{
printf("Usage: resize factor infile outfile\n");
return 1;
}
// remember arguments
int factor = atoi(argv[1]);
char* infile = argv[2];
char* outfile = argv[3];
// open input & output files
FILE* inptr = fopen(infile, "r");
if (inptr == NULL)
{
printf("Could not open %s.\n", infile);
return 2;
}
FILE* outptr = fopen(outfile, "w");
if (outptr == NULL)
{
fclose(inptr);
fprintf(stderr, "Could not create %s.\n", outfile);
return 3;
}
if ((factor <= 0) || (factor > 100))
{
fprintf(stderr, "Factor must be in 1 - 100 range\n");
return 4;
}
// read infile's BITMAPFILEHEADER
BITMAPFILEHEADER bf;
fread(&bf, sizeof(BITMAPFILEHEADER), 1, inptr);
// read infile's BITMAPINFOHEADER
BITMAPINFOHEADER bi;
fread(&bi, sizeof(BITMAPINFOHEADER), 1, inptr);
BITMAPFILEHEADER bfo = bf;
BITMAPINFOHEADER bio = bi;
if (factor == 1)
{
bfo = bf;
bio = bi;
}
else
{
bfo = bf;
bio = bi;
bio.biWidth = bi.biWidth * factor;
bio.biHeight = bi.biHeight * factor;
int padding = (4 - (bio.biWidth * sizeof(RGBTRIPLE)) % 4) % 4;
bio.biSizeImage = (bio.biWidth * abs(bio.biHeight) * 3) + (padding * bio.biWidth);
bfo.bfSize = bio.biSizeImage + HEADER;
}
// ensure infile is (likely) a 24-bit uncompressed BMP 4.0
if (bf.bfType != 0x4d42 || bf.bfOffBits != 54 || bi.biSize != 40 ||
bi.biBitCount != 24 || bi.biCompression != 0)
{
fclose(outptr);
fclose(inptr);
fprintf(stderr, "Unsupported file format.\n");
return 5;
}
// write outfile's BITMAPFILEHEADER
fwrite(&bfo, sizeof(BITMAPFILEHEADER), 1, outptr);
// write outfile's BITMAPINFOHEADER
fwrite(&bio, sizeof(BITMAPINFOHEADER), 1, outptr);
// if factor == 1 just copy file
if (factor == 1)
{
// determine padding for scanlines
int padding = (4 - (bi.biWidth * sizeof(RGBTRIPLE)) % 4) % 4;
// iterate over infile's scanlines
for (int i = 0, biHeight = abs(bi.biHeight); i < biHeight; i++)
{
// iterate over pixels in scanline
for (int j = 0; j < bi.biWidth; j++)
{
// temporary storage
RGBTRIPLE triple;
// read RGB triple from infile
fread(&triple, sizeof(RGBTRIPLE), 1, inptr);
// write RGB triple to outfile
fwrite(&triple, sizeof(RGBTRIPLE), 1, outptr);
}
// skip over padding, if any
fseek(inptr, padding, SEEK_CUR);
// then add it back (to demonstrate how)
for (int k = 0; k < padding; k++)
fputc(0x00, outptr);
}
fclose(inptr);
fclose(outptr);
return 0;
}
else
{
int paddingIn = (4 - (bi.biWidth * sizeof(RGBTRIPLE)) % 4) % 4;
int paddingOut = (4 - (bio.biWidth * sizeof(RGBTRIPLE)) % 4) % 4;
for (int i = 0, biHeight = abs(bi.biHeight); i < biHeight; i++)
{
RGBTRIPLE* buffer = malloc(bi.biWidth * sizeof(RGBTRIPLE));
RGBTRIPLE temp;
for (int j = 0; j < bi.biWidth; j++)
{
fread(&temp, sizeof(RGBTRIPLE), 1, inptr);
buffer[j] = temp;
}
for (int k = 0; k < bi.biWidth; k++)
for (int l = 0; l < factor; l++)
fwrite(&buffer[k], sizeof(RGBTRIPLE), 1, outptr);
for (int k = 0; k < paddingOut; k++)
fputc(0x00, outptr);
fseek(inptr, paddingIn, SEEK_CUR);
free(buffer);
}
}
fclose(inptr);
fclose(outptr);
return 0;
}
Here's the output of a sample run with resizing factor of 2: http://www.putlocker.com/file/6919273A6F21E25D
I'm almost sure the problem is with my looping constructs, and I've been using xxd and gdb for the last 3 hours trying to figure out what's wrong to no avail, any help will be appreciated... thanks.