Bee Eee Blog

I remember the first time I saw the Mandelbrot set.  It was incredible!  After I had successfully programmed at it on my 8088 (a very old DOS computer).  I would wait 10 minutes at a time for a screen to pop up.  The detail was nothing short of amazing.  The swirls, the shapes, the colors.  The neatest thing was the ability to zoom into it to reveal more and more and more detail.

Well it’s been many years and computers have improved a great deal as have the tools to program them.  So I wrote another Mandelbrot explorer.

What is the Mandelbrot set? Well….  In short it is X_n+1 = X_n² + C iterated until the magnitude of X_n is greater than 4 or the maximum number of iterations is met then the number of iterations is used as the color of the pixel.  X_n is a complex number, C is another complex number where the x coordinate of the pixel defines the real part and the y coordinate defines the imaginary part of the number. The magnitude is defined as X² + Absolute Value of (X_i²).  Then this process is repeated for each pixel.  Holy smoke that is a mouthful!

Anyway take a peek at the code if you’d like and surely get the app and have fun exploring the Mandelbrot set.

To zoom in a spot just click on it.  The number is the number of iterations.  The more iterations the deeper the pattern goes (well until you run into percision problems).

Mandelbrot Executable

Mandelbrot source code.

Have fun!

I recently was getting greatly annoyed with some drawing code in my program.  I was drawing a photo that I could zoom and move around.  When I zoomed with the wheel though it would briefly draw the image in two positions.  The first position after it was zoomed, and the second position after it was re-centered on the screen.  Well this looked awful.  Not exactly professional looking.  So I tried a hundered different things.  I tried setting a bool variable in the control to tell the paint function not to draw.  No good.  The drawing was done with asynchronous messages.  Then I tried  BeginInvoke.  That didn’t work also.  I tried SuspendLayout and ResumeLayout functions of the Control class:  No good.  Finally I just used the Visible property which kind of worked, well I didn’t get the double picture, but my background was light color and the foreground dark, so there was still a bad looking flicker.  After a couple of hours I finally found the solution at: http://weblogs.asp.net/jdanforth/archive/2004/03/12/88458.aspx. I worked on the example a little and boiled it down to two functions: StopDrawing and StartDrawing.

The techinque basically turns of drawing and events to the object on the win32 level underneath .Net.  This is very handy and it worked very very well.  Here is the code.

        using System.Runtime.InteropServices;
        private const int WM_SETREDRAW      = 0x000B;
        private const int WM_USER           = 0x400;
        private const int EM_GETEVENTMASK   = (WM_USER + 59);
        private const int EM_SETEVENTMASK   = (WM_USER + 69);

        [DllImport("user32", CharSet = CharSet.Auto)]
        private extern static IntPtr SendMessage(IntPtr hWnd, int msg, int wParam, IntPtr lParam);

        IntPtr eventMask = IntPtr.Zero;

        public void StopDrawing()
        {
            if (drawStopCount == 0)
            {
                // Stop redrawing:
                SendMessage(this.Handle, WM_SETREDRAW, 0, IntPtr.Zero);
                // Stop sending of events:
                eventMask = SendMessage(this.Handle, EM_GETEVENTMASK, 0, IntPtr.Zero);
            }
            drawStopCount++;
        }

        public void StartDrawing()
        {
            drawStopCount--;
            if (drawStopCount == 0)
            {
                // turn on events
                SendMessage(this.Handle, EM_SETEVENTMASK, 0, eventMask);

                // turn on redrawing
                SendMessage(this.Handle, WM_SETREDRAW, 1, IntPtr.Zero);

                Invalidate();
                Refresh();
            }
        }

Here is a little nice bit of code to get text to jump out at you no matter what the background.  Outlined text is especially useful when putting text on an image and don’t have control of the background contrast. Basically it draws a black boarder with a while fill.

// prepare to draw text

StringFormat sf = new StringFormat();

sf.Alignment = StringAlignment.Center;

sf.LineAlignment = StringAlignment.Center;// draw the text to a path

System.Drawing.Drawing2D.GraphicsPath path = new System.Drawing.Drawing2D.GraphicsPath();

path.AddString(text, Font.FontFamily, 0, 14.0f, fillRect, sf);

// fill in the outline

g.FillPath(Brushes.White, path);

// draw the outline

g.DrawPath(new Pen(Color.Black,2.0f) , path);

public static ImageArray LoadTiff(String Image_Path)
{
    ImageArray arr = null;
    unsafe
    {
        UInt32 w = 0;
        UInt32 h = 0;
        uint samples = 3;
        uint bits = 8;
        int i, j, ptr, lptr;

        int tif = TIFFOpen(Image_Path, "r");

        if (0 != tif)
        {
            TIFFGetField(tif, TIFFTAG_IMAGEWIDTH, ref w);
            TIFFGetField(tif, TIFFTAG_IMAGELENGTH, ref h);
            TIFFGetField(tif, TIFFTAG_BITSPERSAMPLE, ref bits);
            TIFFGetField(tif, TIFFTAG_SAMPLESPERPIXEL, ref samples);
            arr = new ImageArray((int)w, (int)h);

            // make sure we get all of the data.
            if (bits == 16)
            {
                UInt32 size = w;
                ushort* raster = (ushort *)_TIFFmalloc((uint)(size * sizeof(ushort) * samples));
                // read in all of the lines
                for (j = 0; j < h; j++)
                {
                    TIFFReadScanline(tif, (byte *)raster, j, 0);
                    // copy line into data
                    for (i = 0, ptr=0; i < w; i++, ptr+=(int)samples)
                    {
                        if (samples == 3)
                        {
                            arr.Data[i + j * w].SetPixel(raster[i], raster[i + 1], raster[i + 2]);
                        }
                        else
                        {
                            ushort val = raster[i + samples - 1];
                            arr.Data[i + j * w].SetPixel(val,val,val);
                        }
                    }
                }

                _TIFFfree((byte *)raster);
            }
            else
            {
                // anything beside 16 bit
                UInt32 size = h * w;
                byte *raster = _TIFFmalloc( size );
                int val = TIFFReadRGBAImage(tif, w, h, raster, 0);
                // copy image data into a bitmap
                if (val != 0)
                {
                    for (j = 0, ptr = 0, lptr=0; j < h; j++)
                    {
                        for (i = 0; i < w; i++, ptr+=4, ptr++)
                        {
                            arr.Data[ptr].SetPixel((ushort)raster[lptr], (ushort)raster[lptr + 1], (ushort)raster[lptr + 2]);
                        } // for i
                    } // for j
                } // if val

                _TIFFfree(raster);
            }
            TIFFClose(tif);
        } // if tif
    } // unsafe

    return arr;
}

Tiff files are interesting.  They are like the all inclusive file format.  It is an extremely flexible file format that allows for many types of pixel formats that other image formats couldn’t possibly handle.  For instance 16 bits per channel or sample in the Tiff lingo.  Event the possibility of 4 or 5 samples per pixel.  If you wanted you could have a Red, Green, Blue, IR, Alpha channel.  Although software would have a difficult time displaying the image.  Anyway I digress — tiff being somewhat flexible is also some what difficult to manage, this is where libtiff comes in handy.  It handles most of this for us.

The first step is to add using System.Runtime.InteropServices; to you module. Then add the stubs for the libtiff functions as follows:

    static class TiffHandler
    {
        [DllImport("libtiff3.dll")]
        private static extern int TIFFOpen(String image_path, String opts);
        [DllImport("libtiff3.dll")]
        private static extern void TIFFClose(int handle);
        [DllImport("libtiff3.dll")]
        private static extern void TIFFGetField(int handle, uint property, ref UInt32 value );
        [DllImport("libtiff3.dll", CharSet = CharSet.Ansi, CallingConvention = CallingConvention.Cdecl)]
        private static extern int TIFFSetField(int handle, uint property, uint value);
        [DllImport("libtiff3.dll", CharSet = CharSet.Ansi, CallingConvention = CallingConvention.Cdecl)]
        private static extern int TIFFSetField(int handle, uint property, string value);
        [DllImport("libtiff3.dll")]
        private unsafe static extern int TIFFReadRGBAImage(int handle, UInt32 width, UInt32 height, byte *raster, int Unkown);
        [DllImport("libtiff3.dll")]
        private unsafe static extern int TIFFReadEncodedStrip(int handle, int strip, byte* buf, int size);
        [DllImport("libtiff3.dll")]
        private unsafe static extern byte* _TIFFmalloc(UInt32 size);
        [DllImport("libtiff3.dll")]
        private unsafe static extern void _TIFFfree(byte* pointer);
        [DllImport("libtiff3.dll")]
        private unsafe static extern void TIFFWriteEncodedStrip(int handle, int offset, byte* buffer, int size);
        [DllImport("libtiff3.dll")]
        private static extern uint TIFFScanlineSize(int handle);
        [DllImport("libtiff3.dll")]
        private static extern int TIFFDefaultStripSize(int handle, int size);
        [DllImport("libtiff3.dll")]
        private unsafe static extern int TIFFWriteScanline(int handle, byte* buffer, int row, int sample);
        [DllImport("libtiff3.dll")]
        private unsafe static extern int TIFFReadScanline(int handle, byte* data, int row, int sample);

Next we add the constants. I’m not going to add them all there are thousands of them but here is an example of the ones that are used in writting a tiff. If you want more look in the libtiff header files. It seems like it’s in tiff.h

        const uint TIFFTAG_IMAGEWIDTH = 256;	/* image width in pixels */
        const uint TIFFTAG_IMAGELENGTH	= 257;	/* image height in pixels */
        const uint TIFFTAG_BITSPERSAMPLE = 258;	/* bits per channel (sample) */
        const uint TIFFTAG_SAMPLESPERPIXEL = 277;	/* samples per pixel */
        const uint TIFFTAG_COMPRESSION	= 259;	/* data compression technique */
        const uint COMPRESSION_DEFLATE	= 32946;	/* Deflate compression */
        const uint PHOTOMETRIC_RGB = 2;	/* RGB color model */
        const uint TIFFTAG_PLANARCONFIG = 284;	/* storage organization */
        const uint PLANARCONFIG_CONTIG	= 1;	/* single image plane */

And then the code to write out the image to a file:

        public static unsafe void SaveTiff(string fileName, ImageArray array)
        {
            int tif = TIFFOpen(fileName, "w");
            int Samples = 3;

            TIFFSetField(tif, TIFFTAG_IMAGEWIDTH, (uint)array.Width);
            TIFFSetField(tif, TIFFTAG_IMAGELENGTH, (uint)array.Height);
            TIFFSetField(tif, TIFFTAG_COMPRESSION, COMPRESSION_DEFLATE);
            TIFFSetField(tif, TIFFTAG_PLANARCONFIG, PLANARCONFIG_CONTIG);
            TIFFSetField(tif, TIFFTAG_PHOTOMETRIC, PHOTOMETRIC_RGB);
            TIFFSetField(tif, TIFFTAG_BITSPERSAMPLE, 16);
            TIFFSetField(tif, TIFFTAG_SAMPLESPERPIXEL, (uint)Samples);
            TIFFSetField(tif, TIFFTAG_ARTIST, "Bee Eee Inventions, LLC");

            int cnt = array.Width * array.Height;
            int size = (cnt * Samples * sizeof(ushort));
            ushort* buffer;

            buffer = (ushort*)_TIFFmalloc((uint)size);

            // We set the strip size of the file to be size of one row of pixels
            //int RowSize = TIFFDefaultStripSize(tif, array.Width*3);

            // copy data into buffer
            int i,pos,ptr=0;
            for (i = 0, pos = 0; i < cnt; i++, pos += Samples, ptr++)
            {
                buffer[pos] =  (ushort)(array.Data[ptr].r);
                buffer[pos + 1] = (ushort)(array.Data[ptr].g);
                buffer[pos + 2] = (ushort)(array.Data[ptr].b);
            }

            // Write the information to the file
            TIFFWriteEncodedStrip(tif, 0, (byte *)buffer, size);

            TIFFClose(tif);

            _TIFFfree((byte *)buffer);
        }

Enjoy. Next article I’ll show you how to read some tiff files. Opening all tiff files could be difficult. :)

c# and gdi+ have a simple way to control the colors that are drawn. It’s basically a ColorMatrix. It’s a 5×5 matrix that is applied to each color if it is set.

Adjusting brightness is just preforming a translate on the color data, and contrast is preforming a scale on the color. Gamma is a whole different form of transform, but it’s included in ImageAttributes which accepts the ColorMatrix.

So here’s the simple code:

            Bitmap origanalImage;
            Bitmap adjustedImage;
            double brightness = 1.0f; // no change in brightness
            double constrast = 2.0f; // twice the contrast
            double gamma = 1.0f; // no change in gamma

            float adjustedBrightness = brightness - 1.0f;
            // create matrix that will brighten and contrast the image
            float[][] ptsArray ={
                    new float[] {contrast, 0, 0, 0, 0}, // scale red
                    new float[] {0, contrast, 0, 0, 0}, // scale green
                    new float[] {0, 0, contrast, 0, 0}, // scale blue
                    new float[] {0, 0, 0, 1.0f, 0}, // don't scale alpha
                    new float[] {adjustedBrightness, adjustedBrightness, adjustedBrightness, 0, 1}};

            imageAttributes = new ImageAttributes();
            imageAttributes.ClearColorMatrix();
            imageAttributes.SetColorMatrix(new ColorMatrix(ptsArray), ColorMatrixFlag.Default, ColorAdjustType.Bitmap);
            imageAttributes.SetGamma(gamma, ColorAdjustType.Bitmap);
            Graphics g = Graphics.FromImage(adjustedImage);
            g.DrawImage(originalImage, new Rectangle(0,0,adjustedImage.Width,adjustedImage.Height)
                ,0,0,bitImage.Width,bitImage.Height,
                GraphicsUnit.Pixel, imageAttributes);

So there it is. Simple enough isn’t it.

Well I finally had a little time today to work on my terrain generation software. It’s written in C++ using the SDL and SDL_gfx graphics libraries along with the Guichan GUI library. I had a bunch of fun adding relief shading. Basically it lightening or darkening the color based on the derivative (change in elevation). The steeper the positive change in elevation the brighter and the steeper the elevation loss the darker.

Anyway the results were really quite good, even a bit better than I expected. Here is an example:

Flat 2d rendering

3d (orthographic) Rendering of terrain

Anyway if you want to download a copy and try just go to http://bee-eee.com/ it’s under the software/terrain section.