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April 29, 2016 21:26
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Problem "resize" from problem set 4 of CS50x course
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/** | |
* bmp.h | |
* | |
* Computer Science 50 | |
* Problem Set 4 | |
* | |
* BMP-related data types based on Microsoft's own. | |
*/ | |
#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.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; | |
/** | |
* 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; |
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/** | |
* copy.c | |
* | |
* Computer Science 50 | |
* Problem Set 4 | |
* | |
* Copies a BMP piece by piece, just because. | |
*/ | |
#include <stdio.h> | |
#include <stdlib.h> | |
#include "bmp.h" | |
int main(int argc, char* argv[]) | |
{ | |
// ensure proper usage | |
if (argc != 3) | |
{ | |
printf("Usage: ./copy infile outfile\n"); | |
return 1; | |
} | |
// remember filenames | |
char* infile = argv[1]; | |
char* outfile = argv[2]; | |
// open input file | |
FILE* inptr = fopen(infile, "r"); | |
if (inptr == NULL) | |
{ | |
printf("Could not open %s.\n", infile); | |
return 2; | |
} | |
// open output file | |
FILE* outptr = fopen(outfile, "w"); | |
if (outptr == NULL) | |
{ | |
fclose(inptr); | |
fprintf(stderr, "Could not create %s.\n", outfile); | |
return 3; | |
} | |
// read infile's BITMAPFILEHEADER | |
BITMAPFILEHEADER bf; | |
fread(&bf, sizeof(BITMAPFILEHEADER), 1, inptr); | |
// read infile's BITMAPINFOHEADER | |
BITMAPINFOHEADER bi; | |
fread(&bi, sizeof(BITMAPINFOHEADER), 1, inptr); | |
// 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 4; | |
} | |
// write outfile's BITMAPFILEHEADER | |
fwrite(&bf, sizeof(BITMAPFILEHEADER), 1, outptr); | |
// write outfile's BITMAPINFOHEADER | |
fwrite(&bi, sizeof(BITMAPINFOHEADER), 1, outptr); | |
// 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); | |
} | |
} | |
// close infile | |
fclose(inptr); | |
// close outfile | |
fclose(outptr); | |
// that's all folks | |
return 0; | |
} |
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/** | |
* resize.c | |
* | |
* Computer Science 50 | |
* Problem Set 4 | |
* | |
* Resizes a BMP by a given factor. | |
*/ | |
#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 factor and check if it is a positive integer up to 100 | |
int n = atoi(argv[1]); | |
if (n < 1 || n > 100) | |
{ | |
printf("Factor must be 1 <= n <= 100\n"); | |
return 2; | |
} | |
// remember filenames | |
char* infile = argv[2]; | |
char* outfile = argv[3]; | |
// open input file | |
FILE* inptr = fopen(infile, "r"); | |
if (inptr == NULL) | |
{ | |
printf("Could not open %s.\n", infile); | |
return 3; | |
} | |
// open output file | |
FILE* outptr = fopen(outfile, "w"); | |
if (outptr == NULL) | |
{ | |
fclose(inptr); | |
fprintf(stderr, "Could not create %s.\n", outfile); | |
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); | |
// 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 4; | |
} | |
// set output width | |
bi.biWidth = bi.biWidth * n; | |
// determine padding for the output image | |
int padding = (4 - (bi.biWidth * sizeof(RGBTRIPLE)) % 4) % 4; | |
// set output height | |
bi.biHeight = bi.biHeight * n; | |
// set output image size | |
bi.biSizeImage = bi.biSizeImage * n * n; | |
//set output file size | |
bf.bfSize = bi.biHeight * (bi.biWidth + padding); | |
// write outfile's BITMAPFILEHEADER | |
fwrite(&bf, sizeof(BITMAPFILEHEADER), 1, outptr); | |
// write outfile's BITMAPINFOHEADER | |
fwrite(&bi, sizeof(BITMAPINFOHEADER), 1, outptr); | |
// iterate over infile's scanlines | |
for (int i = 0, biHeight = abs(bi.biHeight); i < biHeight; i++) | |
{ | |
FILE* linestart = inptr; | |
// iterate line n times (resize height) | |
for (int h = 0; h < n; h++) | |
{ | |
// 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); | |
// iterate pixel n times (resize width) | |
for (int k = 0; k < n; k++) | |
{ | |
// write RGB triple to outfile | |
fwrite(&triple, sizeof(RGBTRIPLE), 1, outptr); | |
} | |
} | |
// add right amount of padding | |
for (int k = 0; k < padding; k++) | |
{ | |
fputc(0x00, outptr); | |
} | |
inptr = linestart; | |
} | |
} | |
// close infile | |
fclose(inptr); | |
// close outfile | |
fclose(outptr); | |
// that's all folks | |
return 0; | |
} |
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