fast way to create a big bitmap from an array of bitmap?

Question

I have this code,

copy/paste in a new winform app and this will write a file on your desktop if you run it: test123abcd.png

Private Sub Form         


        

Answer 1

wow I like unsafe code when it is worthed, solved my problem with c# in the end

here is the code, which is about 70x faster to the code in my question

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

namespace BmpFile
{
    public class BmpTest
    {
        private const int PixelSize = 4;

        public static long Test(int GridX, int GridY, int SquareSize, Rectangle[][] Rect)
        {
            Bitmap bmp = new Bitmap(GridX * SquareSize, GridY * SquareSize, PixelFormat.Format32bppArgb);
            BitmapData bmd = bmp.LockBits(new Rectangle(0, 0, bmp.Width, bmp.Height),
                                          System.Drawing.Imaging.ImageLockMode.ReadWrite,
                                          bmp.PixelFormat);

            int Stride = bmd.Stride;
            int Height = bmd.Height;
            int Width = bmd.Width;

            int RectFirst = Rect.GetUpperBound(0);
            int RectSecond;
            int Offset1, Offset2, Offset3;
            int i, j, k, l, w, h;
            int FullRow = SquareSize * Stride;
            int FullSquare = SquareSize * PixelSize;

            var sw = System.Diagnostics.Stopwatch.StartNew();
            unsafe
            {
                byte* row = (byte*)bmd.Scan0;

                //draw all rectangles
                for (i = 0; i <= RectFirst; ++i)
                {

                    Offset1 = ((i / GridX) * FullRow) + ((i % GridX) * FullSquare) + 3;
                    RectSecond = Rect[i].GetUpperBound(0);

                    for (j = 0; j <= RectSecond; ++j)
                    {
                        Offset2 = Rect[i][j].X * PixelSize + Rect[i][j].Y * Stride;
                        w=Rect[i][j].Width;
                        h=Rect[i][j].Height;
                        for (k = 0; k <= w; ++k)
                        {
                            Offset3 = k * PixelSize;
                            for (l = 0; l <= h; ++l)
                            {
                                row[Offset1 + Offset2 + Offset3 + (l * Stride)] = 255;
                            }
                        }
                    }
                }

                //invert color
                for (int y = 0; y < Height; y++)
                {
                    Offset1 = (y * Stride) + 3;

                    for (int x = 0; x < Width; x++)
                    {
                        if (row[Offset1 + x * PixelSize] == 255)
                        {
                            row[Offset1 + x * PixelSize] = 0;
                        }
                        else
                        {
                            row[Offset1 + x * PixelSize] = 255;
                        }
                    }
                }
            }
            sw.Stop();

            bmp.UnlockBits(bmd);

            bmp.Save(Environment.GetFolderPath(Environment.SpecialFolder.Desktop) + @"\test.png", ImageFormat.Png);
            bmp.Dispose();

            return sw.ElapsedMilliseconds;
        }
    }
}