/// <summary>
/// Applies the a filter kernel to the specified image.
/// </summary>
/// <param name="image">The image.</param>
/// <param name="kernel">The filter kernel. (Needs to be square.)</param>
/// <param name="wrapMode">The texture address mode.</param>
/// <exception cref="ArgumentNullException">
/// <paramref name="image"/> or <paramref name="kernel"/> is <see langword="null"/>.
/// </exception>
/// <exception cref="ArgumentException">
/// <paramref name="kernel"/> is non-square.
/// </exception>
public static void Convolve(Image image, float[,] kernel, TextureAddressMode wrapMode)
{
if (image == null)
throw new ArgumentNullException("image");
if (kernel == null)
throw new ArgumentNullException("kernel");
if (kernel.GetLength(0) != kernel.GetLength(1))
throw new ArgumentException("Filter kernel needs to be square.", "kernel");
int width = image.Width;
int height = image.Height;
int kernelSize = kernel.GetLength(0);
int kernelOffset = kernelSize / 2;
var tmpImage = new Image(width, height, image.Format);
Buffer.BlockCopy(image.Data, 0, tmpImage.Data, 0, image.Data.Length);
// ReSharper disable AccessToDisposedClosure
using (var tempImage4F = new ImageAccessor(tmpImage))
using (var image4F = new ImageAccessor(image))
{
for (int y = 0; y < height; y++)
#else
Parallel.For(0, height, y =>
{
for (int x = 0; x < width; x++)
{
// Apply 2D kernel at (x, y).
Vector4 color = new Vector4();
for (int row = 0; row < kernelSize; row++)
{
int srcY = y + row - kernelOffset;
for (int column = 0; column < kernelSize; column++)
{
int srcX = x + column - kernelOffset;
color += kernel[row, column] * tempImage4F.GetPixel(srcX, srcY, wrapMode);
}
}
image4F.SetPixel(x, y, color);
}
}
);
}
// ReSharper restore AccessToDisposedClosure
}
private static void Resize2D(Image srcImage, Image dstImage, bool alphaTransparency, TextureAddressMode wrapMode, PolyphaseKernel kernelX, PolyphaseKernel kernelY)
{
var tmpImage = new Image(dstImage.Width, srcImage.Height, srcImage.Format);
// ReSharper disable AccessToDisposedClosure
using (var srcImage4F = new ImageAccessor(srcImage))
using (var tmpImage4F = new ImageAccessor(tmpImage))
using (var dstImage4F = new ImageAccessor(dstImage))
{
// Resize horizontally: srcImage --> tmpImage
{
float scale = (float)tmpImage4F.Width / srcImage4F.Width;
float inverseScale = 1.0f / scale;
for (int y = 0; y < tmpImage4F.Height; y++)
#else
Parallel.For(0, tmpImage4F.Height, y =>
{
// Apply polyphase kernel horizontally.
for (int x = 0; x < tmpImage4F.Width; x++)
{
float center = (x + 0.5f) * inverseScale;
int left = (int)Math.Floor(center - kernelX.Width);
int right = (int)Math.Ceiling(center + kernelX.Width);
Debug.Assert(right - left <= kernelX.WindowSize);
float totalRgbWeights = 0.0f;
Vector4 sum = new Vector4();
for (int i = 0; i < kernelX.WindowSize; i++)
{
Vector4 color = srcImage4F.GetPixel(left + i, y, wrapMode);
//if (Numeric.IsNaN(color.X) || Numeric.IsNaN(color.Y) || Numeric.IsNaN(color.Z) || Numeric.IsNaN(color.W)
// || color.X < 0 || color.Y < 0 || color.Z < 0 || color.W < 0
// || color.X > 1 || color.Y > 1 || color.Z > 1 || color.W > 1)
// Debugger.Break();
const float alphaEpsilon = 1.0f / 256.0f;
float alpha = alphaTransparency ? color.W + alphaEpsilon : 1.0f;
float weight = kernelX.Weights[x, i];
float rgbWeight = weight * alpha;
totalRgbWeights += rgbWeight;
sum.X += color.X * rgbWeight;
sum.Y += color.Y * rgbWeight;
sum.Z += color.Z * rgbWeight;
sum.W += color.W * weight;
//if (Numeric.IsNaN(sum.X) || Numeric.IsNaN(sum.Y) || Numeric.IsNaN(sum.Z) || Numeric.IsNaN(sum.W)
// || sum.X < 0 || sum.Y < 0 || sum.Z < 0 || sum.W < 0
// || sum.X > 1 || sum.Y > 1 || sum.Z > 1 || sum.W > 1)
// Debugger.Break();
}
float f = 1 / totalRgbWeights;
sum.X *= f;
sum.Y *= f;
sum.Z *= f;
//if (Numeric.IsNaN(sum.X) || Numeric.IsNaN(sum.Y) || Numeric.IsNaN(sum.Z) || Numeric.IsNaN(sum.W)
// || sum.X < 0 || sum.Y < 0 || sum.Z < 0 || sum.W < 0
// || sum.X > 1 || sum.Y > 1 || sum.Z > 1 || sum.W > 1)
// Debugger.Break();
tmpImage4F.SetPixel(x, y, sum);
}
}
);
}
// Resize vertically: tmpImage --> dstImage
{
float scale = (float)dstImage4F.Height / tmpImage4F.Height;
float inverseScale = 1.0f / scale;
for (int x = 0; x < dstImage4F.Width; x++)
#else
Parallel.For(0, dstImage4F.Width, x =>
{
// Apply polyphase kernel vertically.
for (int y = 0; y < dstImage4F.Height; y++)
{
float center = (y + 0.5f) * inverseScale;
int left = (int)Math.Floor(center - kernelY.Width);
int right = (int)Math.Ceiling(center + kernelY.Width);
Debug.Assert(right - left <= kernelY.WindowSize);
float totalRgbWeights = 0.0f;
Vector4 sum = new Vector4();
for (int i = 0; i < kernelY.WindowSize; i++)
{
Vector4 color = tmpImage4F.GetPixel(x, left + i, wrapMode);
const float alphaEpsilon = 1.0f / 256.0f;
float alpha = alphaTransparency ? color.W + alphaEpsilon : 1.0f;
float weight = kernelY.Weights[y, i];
float rgbWeight = weight * alpha;
totalRgbWeights += rgbWeight;
sum.X += color.X * rgbWeight;
sum.Y += color.Y * rgbWeight;
sum.Z += color.Z * rgbWeight;
sum.W += color.W * weight;
}
float f = 1 / totalRgbWeights;
sum.X *= f;
sum.Y *= f;
sum.Z *= f;
dstImage4F.SetPixel(x, y, sum);
}
}
);
}
}
// ReSharper restore AccessToDisposedClosure
}