using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

using System.Drawing;
using System.Drawing.Imaging;

namespace ConsoleApplication1 {
    class Program {

        static unsafe void hardlight(byte* topColor, byte* botcolor, byte* outColor) {
            overlay(botcolor, topColor, outColor);
        }

        static unsafe void overlay(byte* topData, byte* botData, byte* outData) {
            outData[3] = topData[3];
            float inA = topData[3] / 255f;
            float layerA = botData[3] / 255f;

            float compAlpha = Math.Min(inA, layerA);

            float newAlpha = inA + (1f - inA) * compAlpha;

            if (compAlpha != 0 && newAlpha != 0) {
                float ratio = compAlpha / newAlpha;
                for (int i = 0; i < 3; i++) {
                    float top = topData[i] / 255f;
                    float bot = botData[i] / 255f;

                    float c;
                    if (bot > 0.5f) {
                        float value = (1f - bot) / 0.5f;
                        float min = bot - (1f - bot);
                        c = top * value + min;
                    }
                    else {
                        float value = bot / 0.5f;
                        c = top * value;
                    }
                    c = (c * ratio) + (top * (1f - ratio));
                    outData[i] = (byte) Math.Max(0, Math.Min(255, (int)Math.Floor(c * 255)));
                }
            }
            else {
                for (int i = 0; i < 3; i++) {
                    outData[i] = botData[i];
                }
            }
        }

        static unsafe void hardlightImage(BitmapData topBmd, BitmapData botBmd, BitmapData outBmd) {
            int w = outBmd.Width;
            int h = outBmd.Height;

            byte* topP = (byte*)topBmd.Scan0.ToPointer();
            byte* botP = (byte*)botBmd.Scan0.ToPointer();
            byte* outP = (byte*)outBmd.Scan0.ToPointer();

            int stride = botBmd.Stride;

            for (int y = 0; y < h; y++) {
                for (int x = 0; x < w; x++) {
                    int i = y * stride + x * 4;

                    byte* top = topP + i;
                    byte* bot = botP + i;
                    byte* o = outP + i;

                    hardlight(top, bot, o);
                }
            }
        }

        static void Main(string[] args) {
            Bitmap asuka = Bitmap.FromFile("AsukaBG.png") as Bitmap;
            Bitmap color = Bitmap.FromFile("colora.png") as Bitmap;

            Bitmap output = new Bitmap(asuka.Width, asuka.Height);
            Rectangle bounds = new Rectangle(0, 0, output.Width, output.Height);

            BitmapData asukaBmd = asuka.LockBits(bounds, ImageLockMode.ReadOnly, PixelFormat.Format32bppArgb);
            BitmapData colorBmd = color.LockBits(bounds, ImageLockMode.ReadOnly, PixelFormat.Format32bppArgb);
            BitmapData outBmd = output.LockBits(bounds, ImageLockMode.WriteOnly, PixelFormat.Format32bppArgb);

            int loops = 10;
            long start = DateTime.Now.Ticks / TimeSpan.TicksPerMillisecond;
            for(int i=0; i < loops; i++) {
                hardlightImage(colorBmd, asukaBmd, outBmd);
            }
            long end = DateTime.Now.Ticks / TimeSpan.TicksPerMillisecond;
            // Per loop, ~220ms
            Console.WriteLine("Took {0}ms for {1} loops, that is {2}ms per loop", end-start, loops, (end- start)/(float)loops);

            // Release memory
            asuka.UnlockBits(asukaBmd);
            color.UnlockBits(colorBmd);
            output.UnlockBits(outBmd);

            output.Save("hardlight.png");

            Console.ReadLine();
        }
    }
}