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steganography.c
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steganography.c
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/************************************************************************
**
** NAME: steganography.c
**
** DESCRIPTION: CS61C Fall 2020 Project 1
**
** AUTHOR: Dan Garcia - University of California at Berkeley
** Copyright (C) Dan Garcia, 2020. All rights reserved.
** Justin Yokota - Starter Code
** YOUR NAME HERE
**
** DATE: 2020-08-23
**
**************************************************************************/
#include <stdio.h>
#include <stdlib.h>
#include <inttypes.h>
#include "imageloader.h"
//Determines what color the cell at the given row/col should be. This should not affect Image, and should allocate space for a new Color.
Color *evaluateOnePixel(Image *image, int row, int col)
{
Color *result_color = (Color *) malloc(sizeof(Color));
if (result_color == NULL) exit(-1);
uint8_t B_value = image->image[row][col].B;
if (B_value & 1) {
result_color->R = 0;
result_color->G = 0;
result_color->B = 0;
} else {
result_color->R = 255;
result_color->G = 255;
result_color->B = 255;
}
return result_color;
}
//Given an image, creates a new image extracting the LSB of the B channel.
Image *steganography(Image *image)
{
Image *decoded_image = (Image *) malloc(sizeof(Image));
if (decoded_image == NULL) exit(-1);
Color *decoded_pixel = NULL;
uint32_t i = 0, j = 0, rows = image->rows, cols = image->cols;
decoded_image->image = (Color **) malloc(sizeof(Color *) * rows);
if (decoded_image->image == NULL) exit(-1);
decoded_image->rows = image->rows;
decoded_image->cols = image->cols;
for (i = 0; i < image->rows; ++i) {
Color *pixel_row = (Color *) malloc(sizeof(Color) * cols);
if (pixel_row == NULL) exit(-1);
for (j = 0; j < image->cols; ++j) {
decoded_pixel = evaluateOnePixel(image, i, j);
pixel_row[j] = *decoded_pixel;
free(decoded_pixel);
}
decoded_image->image[i] = pixel_row;
}
return decoded_image;
}
/*
Loads a file of ppm P3 format from a file, and prints to stdout (e.g. with printf) a new image,
where each pixel is black if the LSB of the B channel is 0,
and white if the LSB of the B channel is 1.
argc stores the number of arguments.
argv stores a list of arguments. Here is the expected input:
argv[0] will store the name of the program (this happens automatically).
argv[1] should contain a filename, containing a file of ppm P3 format (not necessarily with .ppm file extension).
If the input is not correct, a malloc fails, or any other error occurs, you should exit with code -1.
Otherwise, you should return from main with code 0.
Make sure to free all memory before returning!
*/
int main(int argc, char **argv)
{
Image *image = NULL;
Image *decoded_image = NULL;
char *filename;
if (argc != 2) {
printf("usage: %s filename\n", argv[0]);
printf("filename is an ASCII PPM file (type P3) with maximuum value 255.\n");
exit(-1);
}
filename = argv[1];
image = readData(filename);
decoded_image = steganography(image);
writeData(decoded_image);
freeImage(image);
freeImage(decoded_image);
return 0;
}