Added comments to save_bmp

Implementierung/main.c

@@ -202,69 +202,84 @@ int main(int argc, char** argv)
 
 
 void save_bmp(const char *filename, unsigned char *img, size_t width, ssize_t height) {
+    // Open a file at the filepath given as a stream in the program
     FILE *fptr = fopen(filename,"wb");
-    if(fptr == NULL) {
+
+    if(fptr == NULL) { // Chech for errors with opening the file stream
         fprintf(stderr,"ERROR: Could not open output file at %s\n.",filename);
         exit(EXIT_FAILURE);
     }
-    int actual_height = (height < 0) ? -height : height;
-    size_t row_padding = (4 - (width) * 3 % 4) % 4;
-    size_t row_width = width * 3 + row_padding;
+
+
+    int actual_height = (height < 0) ? -height : height; // Calculate absolute height for iteration and calculation purposes
+    size_t row_padding = (4 - (width) * 3 % 4) % 4; // Calculate padding for each row as .bmp is 4 bytes aligned
+    size_t row_width = width * 3 + row_padding; // Calculate row width with padding
 
     size_t image_size = actual_height * row_width;
-    size_t file_size = image_size + 54;
+    size_t file_size = image_size + 54; // File size = Image Size + Headers
 
-    unsigned char file_header[14] = {
-        'B', 'M',           
-        0, 0, 0, 0,         
-        0, 0, 0, 0,         
-        54, 0, 0, 0         
+    // File header - contains information about the file
+    unsigned char file_header[14] = { 
+        'B', 'M',           // BM - identifies file as a .bmp file
+        0, 0, 0, 0,         // 4 bytes for file size - will be set later
+        0, 0, 0, 0,         // Reserved
+        54, 0, 0, 0         // 4 bytes that specify the offset where the image array begins
     };
 
-    file_header[2] = (unsigned char)(file_size);
+    // Serialize the size into 4 bytes - (unsigned char) takes only bottom 4 bytes
+    file_header[2] = (unsigned char)(file_size); 
     file_header[3] = (unsigned char)(file_size >> 8);
     file_header[4] = (unsigned char)(file_size >> 16);
     file_header[5] = (unsigned char)(file_size >> 24);
 
-    unsigned char info_header[40] = {
-        40, 0, 0, 0,        
-        0, 0, 0, 0,         
-        0, 0, 0, 0,         
-        1, 0,               
-        24, 0,              
-        0, 0, 0, 0,         
-        0, 0, 0, 0,         
-        0x13, 0x0B, 0, 0,   
-        0x13, 0x0B, 0, 0,   
-        0, 0, 0, 0,         
-        0, 0, 0, 0          
+    // Info header - contains information about the image itself
+    unsigned char info_header[40] = { 
+        40, 0, 0, 0,        // Size of this header    
+        0, 0, 0, 0,         // Width in pixels - set later
+        0, 0, 0, 0,         // Height in pixels - set later
+        1, 0,               // Number of color planes - always 1
+        24, 0,              // Number of bits per pixel or color depth
+        0, 0, 0, 0,         // Compression method - 0 for no compression
+        0, 0, 0, 0,         // Image size - set later
+        0x13, 0x0B, 0, 0,   // Horizontal resolution in pixels per metre - Set to standart 72 pixels per inch
+        0x13, 0x0B, 0, 0,   // Vertical resolution in pixels per metre - Set to standart 72 pixels per inch
+        0, 0, 0, 0,         // Number of colors in the color pallete - 0 for default of 2^n where n is bits per pixel
+        0, 0, 0, 0          // Number of important colors - 0 for all colors important
     };
 
+    // Setting width
     info_header[4] = (unsigned char)(width);
     info_header[5] = (unsigned char)(width >> 8);
     info_header[6] = (unsigned char)(width >> 16);
     info_header[7] = (unsigned char)(width >> 24);
 
+    // Setting height
     uint32_t h = (uint32_t)height; 
     info_header[8] = (unsigned char)(h);
     info_header[9] = (unsigned char)(h >> 8);
     info_header[10] = (unsigned char)(h >> 16);
     info_header[11] = (unsigned char)(h >> 24);
 
+    // Setting image size
     info_header[20] = (unsigned char)(image_size);
     info_header[21] = (unsigned char)(image_size >> 8);
     info_header[22] = (unsigned char)(image_size >> 16);
     info_header[23] = (unsigned char)(image_size >> 24);
 
-    fwrite(file_header,1,14,fptr);
+    // Write headers into file
+    //size_t fwrite(const void ptr[restrict .size * .n], size_t size, size_t n, FILE *restrict stream);
+    fwrite(file_header,1,14,fptr); 
     fwrite(info_header,1,40,fptr);
 
-    unsigned char padding_bytes[3] = {0, 0, 0};
+    // Save padding bytes as array so we can write from it easily to the file later
+    unsigned char padding_bytes[3] = {0, 0, 0}; 
 
     for(int i = 0; i < actual_height; i++) {
-        fwrite(img + (i * width * 3), 3, width, fptr);
+        // Write whole row of pixels - img + (i * width * 3) is the position of the row in the image array
+        // size = 3 as we are interpreting every pixel as an object
+        fwrite(img + (i * width * 3), 3, width, fptr); 
         if(row_padding > 0) {
-            fwrite(padding_bytes,1,row_padding,fptr);
+            fwrite(padding_bytes,1,row_padding,fptr); // Write row_padding number of padding bytes to the file stream
         }
     }