main.cpp - Color Gradient

#include <iostream>
#include <stdint.h>
#include <string>

#define TGA_CMP_HEADER_LEN  (12)

static char tga_header[TGA_CMP_HEADER_LEN] = { 0x0, 0x0, 0x2, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0 };

int main()
{
    unsigned short i, j;
    wchar_t buf[512];
    std::wstring output_file_name;
    unsigned __int32 out_file_id = 0, progress = 0;
    struct Pixel
    {
        unsigned char blue, green, red;
    } pixel_data;
    unsigned char color_buf;
    FILE *w_file = NULL;
    struct IHDR_chunk
    {
        unsigned short width, height;
        unsigned char bpp, dummy;
    } ihdr_chunk_buffer;
    ihdr_chunk_buffer.width = 0;
    ihdr_chunk_buffer.height = 0;
    ihdr_chunk_buffer.bpp = sizeof(Pixel) * 8;
    ihdr_chunk_buffer.dummy = 0;
    while (!ihdr_chunk_buffer.width)
    {
        std::wcout << L"Please choose a width for the color gradient to generate: ";
        memset(buf, 0, sizeof(wchar_t) * 512);
        std::wcin >> buf;
        ihdr_chunk_buffer.width = _wtoi(buf);
        std::wcout << L"\n\n";
    }
    while (!ihdr_chunk_buffer.height)
    {
        std::wcout << L"Now choose a height for the color gradient to generate: ";
        memset(buf, 0, sizeof(wchar_t) * 512);
        std::wcin >> buf;
        ihdr_chunk_buffer.height = _wtoi(buf);
        std::wcout << L"\n\n";
    }
    std::wcout << L"Generating ";
    while (true)
    {
        output_file_name = L"color_gradient_";
        output_file_name += std::to_wstring(out_file_id);
        output_file_name += L".tga";
        _wfopen_s(&w_file, output_file_name.c_str(), L"rb");
        if (w_file)
        {
            fclose(w_file);
            out_file_id++;
        }
        else
        {
            _wfopen_s(&w_file, output_file_name.c_str(), L"wb");
            break;
        }
    }
    std::wcout << L'\"' << output_file_name << L"\"...";
    fwrite(tga_header, sizeof(char), TGA_CMP_HEADER_LEN, w_file);
    fwrite(&ihdr_chunk_buffer, sizeof(IHDR_chunk), 1, w_file);
    for (i = 0; i != ihdr_chunk_buffer.height; i++)
    {
        for (j = 0; j != ihdr_chunk_buffer.width; j++)
        {
            // Human Eye
            pixel_data.green = ((unsigned char)((~((j * 0xFF) / ihdr_chunk_buffer.width)) & 0xFF));
            color_buf = ((unsigned char)(((i * 0xFF) / ihdr_chunk_buffer.height) & 0xFF));
            pixel_data.green = (pixel_data.green <= color_buf) ? 0x0 : (pixel_data.green - color_buf);

            pixel_data.red = ((unsigned char)((~((j * 0xFF) / ihdr_chunk_buffer.width)) & 0xFF));
            color_buf = ((unsigned char)((~((i * 0xFF) / ihdr_chunk_buffer.height)) & 0xFF));
            pixel_data.red = (pixel_data.red <= color_buf) ? 0x0 : (pixel_data.red - color_buf);

            pixel_data.blue = ((unsigned char)(((j * 0xFF) / ihdr_chunk_buffer.width) & 0xFF));
            color_buf = ((unsigned char)(((i * 0xFF) / ihdr_chunk_buffer.height) & 0xFF));
            pixel_data.blue = (pixel_data.blue <= color_buf) ? 0x0 : (pixel_data.blue - color_buf);

            fwrite(&pixel_data, sizeof(Pixel), 1, w_file);
        }
    }
    fclose(w_file);
    return 0;
}