public static unsafe SKPixmap ToSKPixmap(this ComplexImage complexImage, SKImage image)
{
SKPixmap pixmap = image.PeekPixels();
byte * bmpPtr = (byte *)pixmap.GetPixels().ToPointer();
int width = image.Width;
int height = image.Height;
Complex[,] data = complexImage.Data;
double scale = (complexImage.IsFourierTransformed) ? Math.Sqrt(width * height) : 1;
bmpPtr = (byte *)pixmap.GetPixels().ToPointer();
for (int row = 0; row < height; row++)
{
for (int col = 0; col < width; col++)
{
// Assuming SKColorType.Rgba8888 - used by iOS and Android
// (UWP uses SKColorType.Bgra8888)
byte result = (byte)Math.Max(0, Math.Min(255, data[row, col].Magnitude * scale * 255));
* bmpPtr++ = result; // red
* bmpPtr++ = result; // green
* bmpPtr++ = result; // blue
bmpPtr += 1; // Ignore alpha
}
}
return(pixmap);
}
static unsafe ComplexImage ToComplexImage(this SKImage image)
{
SKPixmap pixmap = image.PeekPixels();
byte * bmpPtr = (byte *)pixmap.GetPixels().ToPointer();
int width = image.Width;
int height = image.Height;
if ((!MathHelpers.IsPowerOf2(width)) || (!MathHelpers.IsPowerOf2(height)))
{
throw new ArgumentException("Image width and height must be a power of 2.");
}
ComplexImage complexImage = new ComplexImage(width, height);
Complex[,] data = complexImage.Data;
for (int row = 0; row < height; row++)
{
for (int col = 0; col < width; col++)
{
byte red = *bmpPtr++;
byte green = *bmpPtr++;
byte blue = *bmpPtr++;
bmpPtr += 1; // Ignore alpha
// Assuming SKColorType.Rgba8888 - used by iOS and Android
// (UWP uses SKColorType.Bgra8888)
byte result = (byte)(0.2126 * red + 0.7152 * green + 0.0722 * blue);
data[row, col].Re = (float)result / 255;
}
}
return(complexImage);
}
public void Apply(ComplexImage complexImage)
{
if (!complexImage.IsFourierTransformed)
{
throw new ArgumentException("The source complex image should be Fourier transformed.");
}
int width = complexImage.Width;
int height = complexImage.Height;
int halfWidth = width >> 1;
int halfHeight = height >> 1;
int min = frequencyRange.Min;
int max = frequencyRange.Max;
Complex[,] data = complexImage.Data;
for (int i = 0; i < height; i++)
{
int y = i - halfHeight;
for (int j = 0; j < width; j++)
{
int x = j - halfWidth;
int d = (int)Math.Sqrt(x * x + y * y);
if ((d > max) || (d < min))
{
data[i, j].Re = 0;
data[i, j].Im = 0;
}
}
}
}
public static unsafe SKPixmap FrequencyFilter(this SKImage image, int min, int max)
{
ComplexImage complexImage = image.ToComplexImage();
complexImage.FastFourierTransform();
FrequencyFilter filter = new FrequencyFilter(new FrequencyRange(min, max));
filter.Apply(complexImage);
complexImage.ReverseFastFourierTransform();
SKPixmap pixmap = complexImage.ToSKPixmap(image);
return(pixmap);
}
