public static BitmapSource GetBitmap()
{
const int widthheight = 256;
const float innerRadiusRatio2 = 0.25f;
float mid = (widthheight - 1) / 2f;
float r2max = mid * mid;
float r2min = r2max * innerRadiusRatio2;
var wbitmap = new WriteableBitmap(widthheight, widthheight, 96, 96, PixelFormats.Bgra32, null);
byte[] pixels = new byte[widthheight * widthheight * 4];
// The bitmap is already by default transparent
for (int row = 0; row < widthheight; ++row)
{
for (int col = 0; col < widthheight; ++col)
{
var dx = col - mid;
var dy = row - mid;
var r2 = dx * dx + dy * dy;
if (r2 < r2min || r2 > r2max)
{
continue;
}
int idx = (row * widthheight + col) * 4;
// calculate angle
var phi = (Math.Atan2(dy, dx) / (2 * Math.PI));
if (phi < 0)
{
phi += 1;
}
// calculate color
AxoColor.FromHue((float)phi, out var red, out var green, out var blue);
pixels[idx + 0] = blue; // B
pixels[idx + 1] = green; // G
pixels[idx + 2] = red; // R
pixels[idx + 3] = 255; // A
}
}
// Update writeable bitmap with the colorArray to the image.
var rect = new Int32Rect(0, 0, widthheight, widthheight);
int stride = 4 * widthheight;
wbitmap.WritePixels(rect, pixels, stride, 0);
return(wbitmap);
}