[ADD] - Png to BMP

Additionally added a class that converts png back to a bmp format, converting the colour format of the image to proper form.

Author: VerzatileDev

src/converters/png_to_bmp.c

@@ -0,0 +1,123 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <png.h>
+
+int png_to_bmp(const char *input_filename, const char *output_filename)
+{
+    // Open PNG 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;
+    }
+    // Create PNG read struct
+    png_structp png_ptr = png_create_read_struct(PNG_LIBPNG_VER_STRING, NULL, NULL, NULL);
+    if (!png_ptr)
+    {
+        fprintf(stderr, "Error: could not create PNG read struct\n");
+        fclose(input_file);
+        return 1;
+    }
+    // Create PNG info struct
+    png_infop info_ptr = png_create_info_struct(png_ptr);
+    if (!info_ptr)
+    {
+        fprintf(stderr, "Error: could not create PNG info struct\n");
+        png_destroy_read_struct(&png_ptr, NULL, NULL);
+        fclose(input_file);
+        return 1;
+    }
+    // Set error handling
+    if (setjmp(png_jmpbuf(png_ptr)))
+    {
+        fprintf(stderr, "Error: PNG error\n");
+        png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
+        fclose(input_file);
+        return 1;
+    }
+    // Initialize PNG I/O
+    png_init_io(png_ptr, input_file);
+    // Read PNG header info
+    png_read_info(png_ptr, info_ptr);
+    // Get PNG image attributes
+    int width = png_get_image_width(png_ptr, info_ptr);
+    int height = png_get_image_height(png_ptr, info_ptr);
+    int color_type = png_get_color_type(png_ptr, info_ptr);
+    int bit_depth = png_get_bit_depth(png_ptr, info_ptr);
+    // Make sure it's a valid format for conversion
+    if (color_type != PNG_COLOR_TYPE_RGB || bit_depth != 8)
+    {
+        fprintf(stderr, "Error: unsupported PNG format\n");
+        png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
+        fclose(input_file);
+        return 1;
+    }
+    // Allocate memory for PNG image data
+    png_bytep *row_pointers = (png_bytep *)malloc(height * sizeof(png_bytep));
+    if (!row_pointers)
+    {
+        fprintf(stderr, "Error: could not allocate memory for PNG image data\n");
+        png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
+        fclose(input_file);
+        return 1;
+    }
+    for (int y = 0; y < height; y++)
+    {
+        row_pointers[y] = (png_byte *)malloc(png_get_rowbytes(png_ptr, info_ptr));
+        if (!row_pointers[y])
+        {
+            fprintf(stderr, "Error: could not allocate memory for PNG image data\n");
+            for (int i = 0; i < y; i++)
+                free(row_pointers[i]);
+            free(row_pointers);
+            png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
+            fclose(input_file);
+            return 1;
+        }
+    }
+    // Read PNG image data
+    png_read_image(png_ptr, row_pointers);
+    // Close PNG file
+    png_destroy_read_struct(&png_ptr, &info_ptr, NULL);
+    fclose(input_file);
+    // Open BMP 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);
+        for (int y = 0; y < height; y++)
+            free(row_pointers[y]);
+        free(row_pointers);
+        return 1;
+    }
+    // Write BMP header
+    unsigned char header[54] = {
+        'B', 'M', 0, 0, 0, 0, 0, 0, 0, 0, 54, 0, 0, 0, 40, 0,
+        0, 0, (unsigned char)(width), (unsigned char)(width >> 8), (unsigned char)(width >> 16), (unsigned char)(width >> 24),
+        (unsigned char)(height), (unsigned char)(height >> 8), (unsigned char)(height >> 16), (unsigned char)(height >> 24),
+        1, 0, 24, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};
+    fwrite(header, sizeof(unsigned char), 54, output_file);
+    // Write BMP image data
+    for (int y = height - 1; y >= 0; y--)
+    {
+        for (int x = 0; x < width; x++)
+        {
+            png_bytep pixel = &(row_pointers[y][x * 3]);
+            fwrite(&pixel[2], sizeof(png_byte), 1, output_file);
+            fwrite(&pixel[1], sizeof(png_byte), 1, output_file);
+            fwrite(&pixel[0], sizeof(png_byte), 1, output_file);
+        }
+        // Add padding
+        for (int p = 0; p < (4 - (width * 3) % 4) % 4; p++)
+            fputc(0, output_file);
+    }
+    // Close BMP file
+    fclose(output_file);
+    // Free memory
+    for (int y = 0; y < height; y++)
+        free(row_pointers[y]);
+    free(row_pointers);
+    printf("Converted %s to %s\n", input_filename, output_filename);
+    return 0;
+}

src/main.c

@@ -1,12 +1,14 @@
 #include "gtk_gui.c"
 //#include "converters/bmp_to_jpeg.c" // Include this line to test the bmp_to_jpeg function
 //#include "converters/bmp_to_png.c"
+//#include "converters/png_to_bmp.c"
 
 int main(int argc, char **argv)
 {
     //Include the following line to test the bmp_to_jpeg function
     //bmp_to_jpeg("assets/images/test_image.bmp", "assets/images/testjpg.jpg");
     //bmp_to_png("assets/images/test_image_negative.bmp", "assets/images/testpng.png");
+    //png_to_bmp("assets/images/testpng.png", "assets/images/test_i.bmp");
 
     GtkApplication *app;
     int status;