Iterate over image pixels and rotate Colors

Question

I want to be able to iterate over the bitmap and increment the value by one, but currently the image is coming back from a lower quality memory stream than before, and the change is not smooth at all.

    private static Bitmap CyclePalette(Bitmap original)
    {
        using (var bitMapStream = new MemoryStream())
        {
            original.Save(bitMapStream, format: ImageFormat.Gif);
            var newBitmap = new Bitmap(bitMapStream);

            var newPalette = newBitmap.Palette;

            for (var i = 0; i < newPalette.Entries.Length - 5; i++)
            {

                var oldColor = newPalette.Entries[i];
                newPalette.Entries[i] = newPalette.Entries[i + 1];
                newPalette.Entries[i + 1] = oldColor;

            }
            newBitmap.Palette = newPalette;
            return newBitmap; 
        }
    }

Answer 1

First, let's talk about GIF files and your original solution.

It is very simple to make it work very quickly, but when, for pleasure, I did what I had to laugh - now I know what you mean by quality, degraded .. !!

Let me explain: there are several options in GIF files, but the important thing here is whether it is fading or not.

, 256 ; , , , , GIF : dither , ! , .

, , ; , . , palRotate.

: GIF ARGB-! Ks, . , .

LockBits . PictureBox, a Button a Timer. , PictureBox. testdata 500x500.

using System.Drawing.Imaging;
using System.Runtime.InteropServices;
using System.IO;
//..

// the data array
int[,] Ks;
// the offset for cycling
int koffset = 0;
// a list of colors
List<Color> colors = new List<Color>();

public void paintKs()
{
    if (Ks == null) return;

    Size s1 = pb_image.ClientSize;
    pb_image.Image = new Bitmap(s1.Width, s1.Height);
    Bitmap bmp = new Bitmap(pb_image.Image);

    PixelFormat fmt1 = bmp.PixelFormat;
    byte bpp1 = 4;

    Rectangle rect = new Rectangle(Point.Empty, s1);
    BitmapData bmpData = bmp.LockBits(rect, ImageLockMode.ReadOnly, fmt1);

    int size1 = bmpData.Stride * bmpData.Height;
    byte[] data = new byte[size1];
    System.Runtime.InteropServices.Marshal.Copy(bmpData.Scan0, data, 0, size1);

    for (int y = 0; y < s1.Height; y++)
    {
        for (int x = 0; x < s1.Width; x++)
        {
            int index = y * bmpData.Stride + x * bpp1;
            Color c = colors[(Ks[x, y] + koffset) % (colors.Count)];
            if (Ks[x, y] == 0) c = Color.Black;
            data[index + 0] = c.B;
            data[index + 1] = c.G;
            data[index + 2] = c.R;
            data[index + 3] = 255;
        }
    }

    System.Runtime.InteropServices.Marshal.Copy(data, 0, bmpData.Scan0, data.Length);
    bmp.UnlockBits(bmpData);

    pb_image.Image = bmp;
}

void saveKs(string dataFile)
{
   using (BinaryWriter writer = new BinaryWriter(File.Open(dataFile, FileMode.Create)))
   {
        for (int y = 0; y < Ks.GetLength(0); y++)
            for (int x = 0; x < Ks.GetLength(1); x++)
                writer.Write((Int16)Ks[x, y]);
   }
}

void loadKs(string dataFile)
{
   int w = pb_image.ClientSize.Width;
   if (Ks == null) Ks = new int[w, w];

   using (BinaryReader reader = new BinaryReader(File.Open(dataFile, FileMode.Open)))
   {
        for (int y = 0; y < Ks.GetLength(0); y++)
            for (int x = 0; x < Ks.GetLength(1); x++)
                 Ks[x, y] = reader.ReadInt16();
   }

}

private void Test_Click(object sender, EventArgs e)
{
    loadKs("fractalData021.dat");
    for (int i = 0; i < 256; i++)
    {
        // a very simple and rather awful palette!
        for (int i = 0; i < 256; i++)  
             colors.Add(Color.FromArgb(255, i, i, 255 - i));
        for (int i = 0; i < 100; i++) 
             colors.Add(Color.FromArgb(255, i + 100, 255 -i, 155 - i));
        for (int i = 0; i < 100; i++) 
             colors.Add(Color.FromArgb(255, i + i+ 50, 255 - i - i, 155 - i/2));
    }
    paintKs();
    timer1.Intervall = 33;  // 30 fps
    timer1.Start();
}

private void timer1_Tick(object sender, EventArgs e)
{
    koffset++;
    if (koffset >= colors.Count) koffset = 0;;
    paintKs();
}

; 500x500 :

http://www.file-upload.net/download-9796723/fractalData021.dat.html

http://www.file-upload.net/download-9796722/fractalData021.jpg.html

http://www.file-upload.net/download-9796721/fractalData021.txt.html

Update:

, GIF .

void palRotate()
{
    Bitmap bmp = (Bitmap)pb_image.Image;
    var pal = bmp.Palette;
    for (int i = 0; i < 256; i++)  pal.Entries[(i + koffset) % 256] = colors[i];
    bmp.Palette = pal;
    pb_image.Image = bmp;
}

:

pb_image.Image = new Bitmap("d:\\fff.gif");
Bitmap bmp = (Bitmap)pb_image.Image;
var pal = bmp.Palette;
for (int i = 0; i < 256; i++) colors.Add(pal.Entries[i]);

, , - ; .

, , koffset.

Answer 2

, . , 3 * 85 = 255, 1 Mset. ( struct), , 2 . .

#include <stdio.h>
#include <memory.h>

#define MAXITER 1000   // iteration depth

unsigned char pal [256][3];

int Mandelplot (int x, int y) {
    // return (palette) colour for pixel
    int c, i=iterate (x, y);      // your iteration function
    if (i >= MAXITER)
        c = 255;
     else
        c = i % 255;
    return c;
}

void rotate_palette (void) {
    // leaves index 255 unchanged for Mset pixels
    unsigned char r=pal[0][0], g=pal[0][1], b=pal[0][2];
    memcpy (&pal[0][0], &pal[1][0], 254 * 3 * sizeof(unsigned char));
    pal[254][0] = r;
    pal[254][1] = g;
    pal[254][2] = b;
}

int main (void) {
    unsigned char r=0, g=0, b=255;
    int i;

    for (i=0; i<85; i++) {
        pal [i][0]= r;
        pal [i][1]= g;
        pal [i][2]= b;
        b -= 3;
        g += 3;
    }

    for (i=85; i<170; i++) {
        pal [i][0]= r;
        pal [i][1]= g;
        pal [i][2]= b;
        g -= 3;
        r += 3;
    }

    for (i=170; i<255; i++) {
        pal [i][0]= r;
        pal [i][1]= g;
        pal [i][2]= b;
        r -= 3;
        b += 3;
    }

    pal [255][0] = 0;  // black on the Mset
    pal [255][1] = 0;
    pal [255][2] = 0;

    for (i=0; i<256; i++)
       printf ("%02X %02X %02X, ", pal[i][0], pal[i][1], pal[i][2]);

    return 0;
}