added bmp to jpeg converter

Author: Sommos

src/converters/bmp_to_jpeg.c

@@ -0,0 +1,112 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <jpeglib.h>
+
+int bmp_to_jpeg(int argc, char *argv[])
+{
+    if (argc != 3)
+    {
+        fprintf(stderr, "Usage: %s input.bmp output.jpg\n", argv[0]);
+        return 1;
+    }
+
+    char *input_filename = argv[1];
+    char *output_filename = argv[2];
+
+    // open BMP file for reading
+    FILE *input_file = fopen(input_filename, "rb");
+    if (!input_file)
+    {
+        fprintf(stderr, "Error: could not open input file %s\n", input_filename);
+        return 1;
+    }
+    // read BMP header
+    unsigned char header[54];
+    if (fread(header, sizeof(unsigned char), 54, input_file) != 54)
+    {
+        fprintf(stderr, "Error: invalid BMP file %s\n", input_filename);
+        fclose(input_file);
+        return 1;
+    }
+    // check if BMP file is valid
+    if (header[0] != 'B' || header[1] != 'M')
+    {
+        fprintf(stderr, "Error: invalid BMP file %s\n", input_filename);
+        fclose(input_file);
+        return 1;
+    }
+    // get image width and height from BMP header
+    int width = *(int *)&header[18];
+    int height = *(int *)&header[22];
+    // calculate padding for BMP file
+    int padding = 0;
+    while ((width * 3 + padding) % 4 != 0)
+    {
+        padding++;
+    }
+    // allocate memory for BMP image data
+    unsigned char *bmp_data = (unsigned char *)malloc(width * height * 3 + height * padding);
+    if (!bmp_data)
+    {
+        fprintf(stderr, "Error: could not allocate memory for BMP image data\n");
+        fclose(input_file);
+        return 1;
+    }
+    // read BMP image data
+    if (fread(bmp_data, sizeof(unsigned char), width * height * 3 + height * padding, input_file) != width * height * 3 + height * padding)
+    {
+        fprintf(stderr, "Error: invalid BMP file %s\n", input_filename);
+        free(bmp_data);
+        fclose(input_file);
+        return 1;
+    }
+    // close BMP file
+    fclose(input_file);
+    // allocate memory for JPEG image data
+    unsigned char *jpeg_data = NULL;
+    unsigned long jpeg_size = 0;
+    // create JPEG compressor object
+    struct jpeg_compress_struct cinfo;
+    struct jpeg_error_mgr jerr;
+    cinfo.err = jpeg_std_error(&jerr);
+    jpeg_create_compress(&cinfo);
+    // open output file for writing
+    FILE *output_file = fopen(output_filename, "wb");
+    if (!output_file)
+    {
+        fprintf(stderr, "Error: could not open output file %s\n", output_filename);
+        free(bmp_data);
+        jpeg_destroy_compress(&cinfo);
+        return 1;
+    }
+    // set JPEG compressor parameters
+    cinfo.image_width = width;
+    cinfo.image_height = height;
+    cinfo.input_components = 3;
+    cinfo.in_color_space = JCS_RGB;
+    jpeg_set_defaults(&cinfo);
+    jpeg_set_quality(&cinfo, 75, TRUE);
+    // set output file for JPEG compressor
+    jpeg_stdio_dest(&cinfo, output_file);
+    // start JPEG compressor
+    jpeg_start_compress(&cinfo, TRUE);
+    // write JPEG image data
+    while (cinfo.next_scanline < cinfo.image_height)
+    {
+        JSAMPROW row_pointer = &bmp_data[(cinfo.image_height - cinfo.next_scanline - 1) * (width * 3 + padding)];
+        jpeg_write_scanlines(&cinfo, &row_pointer, 1);
+    }
+    // finish JPEG compressor
+    jpeg_finish_compress(&cinfo);
+    // get size of JPEG image data
+    jpeg_size = ftell(output_file);
+    // close output file
+    fclose(output_file);
+    // destroy JPEG compressor object
+    jpeg_destroy_compress(&cinfo);
+    // free BMP image data
+    free(bmp_data);
+    printf("Converted %s to %s (%lu bytes)\n", input_filename, output_filename, jpeg_size);
+
+    return 0;
+}