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CS50 Problem Set 4
Here’s my answer for the CS50 Problem Set 4. Hope that will help you a bit.
Problem 1: Volume
// Modifies the volume of an audio file
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
// Number of bytes in .wav header
const int HEADER_SIZE = 44;
int main(int argc, char *argv[])
{
// Check command-line arguments
if (argc != 4)
{
printf("Usage: ./volume input.wav output.wav factor\n");
return 1;
}
// Open files and determine scaling factor
FILE *input = fopen(argv[1], "r");
if (input == NULL)
{
printf("Could not open file.\n");
return 1;
}
FILE *output = fopen(argv[2], "w");
if (output == NULL)
{
printf("Could not open file.\n");
return 1;
}
float factor = atof(argv[3]);
// TODO: Copy header from input file to output file
uint8_t header[44];
fread(&header, 44, 1, input);
fwrite(&header, 44, 1, output);
// TODO: Read samples from input file and write updated data to output file
int16_t buffer;
while (fread(&buffer, sizeof(int16_t), 1, input))
{
buffer *= factor;
fwrite(&buffer, sizeof(int16_t), 1, output);
}
// Close files
fclose(input);
fclose(output);
}volume.cProblem 2: Filter
#include "helpers.h"
#include <math.h>
// Convert image to grayscale
void grayscale(int height, int width, RGBTRIPLE image[height][width])
{
int avg = 0;
for (int i = 0; i < height; i++)
{
for (int j = 0; j < width; j++)
{
avg = (int) round((image[i][j].rgbtRed + image[i][j].rgbtGreen + image[i][j].rgbtBlue) /
3.0);
image[i][j].rgbtRed = avg;
image[i][j].rgbtGreen = avg;
image[i][j].rgbtBlue = avg;
}
}
return;
}
// Convert image to sepia
void sepia(int height, int width, RGBTRIPLE image[height][width])
{
for (int i = 0; i < height; i++)
{
for (int j = 0; j < width; j++)
{
int sepiaRed = (int) round(.393 * image[i][j].rgbtRed + .769 * image[i][j].rgbtGreen +
.189 * image[i][j].rgbtBlue);
int sepiaGreen = (int) round(.349 * image[i][j].rgbtRed + .686 * image[i][j].rgbtGreen +
.168 * image[i][j].rgbtBlue);
int sepiaBlue = (int) round(.272 * image[i][j].rgbtRed + .534 * image[i][j].rgbtGreen +
.131 * image[i][j].rgbtBlue);
// sepiaRed = .393 * originalRed + .769 * originalGreen + .189 * originalBlue
// sepiaGreen = .349 * originalRed + .686 * originalGreen + .168 * originalBlue
// sepiaBlue = .272 * originalRed + .534 * originalGreen + .131 * originalBlue
// Make sure that if the value of sepiaRed, sepiaGreen and sepiaBlue exceed 255, their
// value will be capped at 255
if (sepiaRed > 255)
{
sepiaRed = 255;
}
if (sepiaGreen > 255)
{
sepiaGreen = 255;
}
if (sepiaBlue > 255)
{
sepiaBlue = 255;
}
image[i][j].rgbtRed = sepiaRed;
image[i][j].rgbtGreen = sepiaGreen;
image[i][j].rgbtBlue = sepiaBlue;
}
}
return;
}
// Reflect image horizontally
void reflect(int height, int width, RGBTRIPLE image[height][width])
{
int temp_width = 0;
RGBTRIPLE temp[height][width];
if (width % 2 == 0)
{
temp_width = width / 2;
}
else
{
temp_width = (width + 1) / 2;
}
for (int i = 0; i < height; i++)
{
for (int j = 0; j < temp_width; j++)
{
// Swap pixels
temp[i][j] = image[i][j];
image[i][j] = image[i][width - 1 - j];
image[i][width - 1 - j] = temp[i][j];
}
}
return;
}
// Blur image
void blur(int height, int width, RGBTRIPLE image[height][width])
{
// Create a copy of image
RGBTRIPLE copy[height][width];
for (int i = 0; i < height; i++)
{
for (int j = 0; j < width; j++)
{
int tempRed = 0, tempGreen = 0, tempBlue = 0;
float pixel_count = 0;
copy[i][j] = image[i][j];
// get the average of the pixel RGB values
for (int m = i - 1; m <= i + 1; m++)
{
for (int n = j - 1; n <= j + 1; n++)
{
if (m >= 0 && m < height && n >= 0 &&
n < width) // avoiding the pixels that cross the edge
{
tempRed += image[m][n].rgbtRed;
tempGreen += image[m][n].rgbtGreen;
tempBlue += image[m][n].rgbtBlue;
pixel_count += 1;
}
}
}
copy[i][j].rgbtRed = round(tempRed / pixel_count);
copy[i][j].rgbtGreen = round(tempGreen / pixel_count);
copy[i][j].rgbtBlue = round(tempBlue / pixel_count);
}
}
// give the value of copy[i][j] back to image[i][j]
for (int i = 0; i < height; i++)
{
for (int j = 0; j < width; j++)
{
image[i][j] = copy[i][j];
}
}
return;
}filter.cProblem 3: Recover
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
int main(int argc, char *argv[])
{
// Accept a single command-line argument
if (argc != 2)
{
printf("Usage: ./recover FILE\n");
return 1;
}
// Open the memory card
FILE *card = fopen(argv[1], "r");
// Create a buffer for a block of data
uint8_t buffer[512];
int counter = 0;
int found_image = 1;
FILE *img;
char filename[8];
// While there's still data left to read from the memory card
while (fread(buffer, 1, 512, card) == 512)
{
// Create JPEGs from the data
if (buffer[0] == 0xff && buffer[1] == 0xd8 && buffer[2] == 0xff &&
(buffer[3] & 0xf0) == 0xe0)
{
found_image = 0;
}
if (found_image == 0)
{
if (counter != 0)
{
fclose(img);
} // close the previous file and start a new file to write (except the first file)
sprintf(filename, "%03i.jpg", counter);
img = fopen(filename, "w");
fwrite(buffer, 1, 512, img);
counter += 1;
found_image = 1;
}
else if (counter != 0)
// the block does not contain the signature of jpg, so it will be continuously written into
// the previously opened file if the first block does not contain the signature, it won't be
// written to the image
{
fwrite(buffer, 1, 512, img);
}
}
// there's nothing to write, so close all the files
fclose(img);
fclose(card);
}recover.c