filter.c

#include <getopt.h>
#include <stdio.h>
#include <stdlib.h>

#include "helpers.h"

int main(int argc, char *argv[])
{
    // Define allowable filters
    char *filters = "bgrs";

    // Get filter flag and check validity
    char filter = getopt(argc, argv, filters);
    if (filter == '?')
    {
        printf("Invalid filter.\n");
        return 1;
    }

    // Ensure only one filter
    if (getopt(argc, argv, filters) != -1)
    {
        printf("Only one filter allowed.\n");
        return 2;
    }

    // Ensure proper usage
    if (argc != optind + 2)
    {
        printf("Usage: ./filter [flag] infile outfile\n");
        return 3;
    }

    // Remember filenames
    char *infile = argv[optind];
    char *outfile = argv[optind + 1];

    // Open input file
    FILE *inptr = fopen(infile, "r");
    if (inptr == NULL)
    {
        printf("Could not open %s.\n", infile);
        return 4;
    }

    // Open output file
    FILE *outptr = fopen(outfile, "w");
    if (outptr == NULL)
    {
        fclose(inptr);
        printf("Could not create %s.\n", outfile);
        return 5;
    }

    // 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);
        printf("Unsupported file format.\n");
        return 6;
    }

    // Get image's dimensions
    int height = abs(bi.biHeight);
    int width = bi.biWidth;

    // Allocate memory for image
    RGBTRIPLE(*image)[width] = calloc(height, width * sizeof(RGBTRIPLE));
    if (image == NULL)
    {
        printf("Not enough memory to store image.\n");
        fclose(outptr);
        fclose(inptr);
        return 7;
    }

    // Determine padding for scanlines
    int padding = (4 - (width * sizeof(RGBTRIPLE)) % 4) % 4;

    // Iterate over infile's scanlines
    for (int i = 0; i < height; i++)
    {
        // Read row into pixel array
        fread(image[i], sizeof(RGBTRIPLE), width, inptr);

        // Skip over padding
        fseek(inptr, padding, SEEK_CUR);
    }

    // uncomment belows to test a small 3x3 image
    // first row: (10, 20, 30), (40, 50, 60), (70, 80, 90)
    // second row: (110, 130, 140), (120, 140, 150), (130, 150, 160)
    // third row: (200, 210, 220), (220, 230, 240), (240, 250, 255)


    // int red[] = {10, 40, 70, 110, 120, 130, 200, 220, 240};
    // int green[] = {20, 50, 80, 130, 140, 150, 210, 230, 250};
    // int blue[] = {30, 60, 90, 140, 150, 160, 220, 240, 255};
    // int item = 0;

    // RGBTRIPLE pixel[9];

    // RGBTRIPLE(*image_test)[3] = calloc(3, 3 * sizeof(RGBTRIPLE));
    // for (int row = 0; row < 3; ++row)
    // {
    //     for (int col = 0; col < 3; ++col)
    //     {
    //         pixel[item].rgbtRed = red[item];
    //         pixel[item].rgbtGreen = green[item];
    //         pixel[item].rgbtBlue = blue[item];
    //         image_test[row][col] = pixel[item];
    //         item++;
    //     }
    // }

    // height = width = 3;

    // Filter image
    switch (filter)
    {
        // Blur
        case 'b':
            blur(height, width, image);
            break;

        // Grayscale
        case 'g':
            grayscale(height, width, image);
            break;

        // Reflection
        case 'r':
            reflect(height, width, image);
            break;

        // Sepia
        case 's':
            sepia(height, width, image);
            break;
    }

    // Write outfile's BITMAPFILEHEADER
    fwrite(&bf, sizeof(BITMAPFILEHEADER), 1, outptr);

    // Write outfile's BITMAPINFOHEADER
    fwrite(&bi, sizeof(BITMAPINFOHEADER), 1, outptr);

    // Write new pixels to outfile
    for (int i = 0; i < height; i++)
    {
        // Write row to outfile
        fwrite(image[i], sizeof(RGBTRIPLE), width, outptr);

        // Write padding at end of row
        for (int k = 0; k < padding; k++)
        {
            fputc(0x00, outptr);
        }
    }

    // Free memory for image
    free(image);

    // Close files
    fclose(inptr);
    fclose(outptr);
    return 0;
}