void OnCanvasViewPaintSurface(object sender, SKPaintSurfaceEventArgs args)
{
SKImageInfo info = args.Info;
SKSurface surface = args.Surface;
SKCanvas canvas = surface.Canvas;
canvas.Clear();
TaperSide taperSide = (TaperSide)taperSidePicker.SelectedIndex;
TaperCorner taperCorner = (TaperCorner)taperCornerPicker.SelectedIndex;
float taperFraction = (float)taperFractionSlider.Value;
SKMatrix taperMatrix =
TaperTransform.Make(new SKSize(bitmap.Width, bitmap.Height),
taperSide, taperCorner, taperFraction);
// Display the matrix in the lower-right corner
SKSize matrixSize = matrixDisplay.Measure(taperMatrix);
matrixDisplay.Paint(canvas, taperMatrix,
new SKPoint(info.Width - matrixSize.Width,
info.Height - matrixSize.Height));
// Center bitmap on canvas
float x = (info.Width - bitmap.Width) / 2;
float y = (info.Height - bitmap.Height) / 2;
SKMatrix matrix = SKMatrix.MakeTranslation(-x, -y);
SKMatrix.PostConcat(ref matrix, taperMatrix);
SKMatrix.PostConcat(ref matrix, SKMatrix.MakeTranslation(x, y));
canvas.SetMatrix(matrix);
canvas.DrawBitmap(bitmap, x, y);
}
/// <summary>
/// Creates a matrix that performs a tapering projective transform.
/// <see href="https://docs.microsoft.com/en-us/xamarin/xamarin-forms/user-interface/graphics/skiasharp/transforms/non-affine"/>
/// </summary>
/// <param name="size">The rectangular size of the image being transformed.</param>
/// <param name="side">An enumeration that indicates the side of the rectangle that tapers.</param>
/// <param name="corner">An enumeration that indicates on which corners to taper the rectangle.</param>
/// <param name="fraction">The amount to taper.</param>
/// <returns>The <see cref="Matrix4x4"/></returns>
public static Matrix4x4 CreateTaperMatrix(Size size, TaperSide side, TaperCorner corner, float fraction)
{
Matrix4x4 matrix = Matrix4x4.Identity;
/*
* SkMatrix is laid out in the following manner:
*
* [ ScaleX SkewY Persp0 ]
* [ SkewX ScaleY Persp1 ]
* [ TransX TransY Persp2 ]
*
* When converting from Matrix4x4 to SkMatrix, the third row and
* column is dropped. When converting from SkMatrix to Matrix4x4
* the third row and column remain as identity:
*
* [ a b c ] [ a b 0 c ]
* [ d e f ] -> [ d e 0 f ]
* [ g h i ] [ 0 0 1 0 ]
* [ g h 0 i ]
*/
switch (side)
{
case TaperSide.Left:
matrix.M11 = fraction;
matrix.M22 = fraction;
matrix.M14 = (fraction - 1) / size.Width;
switch (corner)
{
case TaperCorner.RightOrBottom:
break;
case TaperCorner.LeftOrTop:
matrix.M12 = size.Height * matrix.M14;
matrix.M42 = size.Height * (1 - fraction);
break;
case TaperCorner.Both:
matrix.M12 = size.Height * .5F * matrix.M14;
matrix.M42 = size.Height * (1 - fraction) / 2;
break;
}
break;
case TaperSide.Top:
matrix.M11 = fraction;
matrix.M22 = fraction;
matrix.M24 = (fraction - 1) / size.Height;
switch (corner)
{
case TaperCorner.RightOrBottom:
break;
case TaperCorner.LeftOrTop:
matrix.M21 = size.Width * matrix.M24;
matrix.M41 = size.Width * (1 - fraction);
break;
case TaperCorner.Both:
matrix.M21 = size.Width * .5F * matrix.M24;
matrix.M41 = size.Width * (1 - fraction) * .5F;
break;
}
break;
case TaperSide.Right:
matrix.M11 = 1 / fraction;
matrix.M14 = (1 - fraction) / (size.Width * fraction);
switch (corner)
{
case TaperCorner.RightOrBottom:
break;
case TaperCorner.LeftOrTop:
matrix.M12 = size.Height * matrix.M14;
break;
case TaperCorner.Both:
matrix.M12 = size.Height * .5F * matrix.M14;
break;
}
break;
case TaperSide.Bottom:
matrix.M22 = 1 / fraction;
matrix.M24 = (1 - fraction) / (size.Height * fraction);
switch (corner)
{
case TaperCorner.RightOrBottom:
break;
case TaperCorner.LeftOrTop:
matrix.M21 = size.Width * matrix.M24;
break;
case TaperCorner.Both:
matrix.M21 = size.Width * .5F * matrix.M24;
break;
}
break;
}
return(matrix);
}
/// <summary> /// Appends a matrix that performs a tapering projective transform. /// </summary> /// <param name="side">An enumeration that indicates the side of the rectangle that tapers.</param> /// <param name="corner">An enumeration that indicates on which corners to taper the rectangle.</param> /// <param name="fraction">The amount to taper.</param> /// <returns>The <see cref="ProjectiveTransformBuilder"/>.</returns> public ProjectiveTransformBuilder AppendTaper(TaperSide side, TaperCorner corner, float fraction) => this.Append(size => TransformUtilities.CreateTaperMatrix(size, side, corner, fraction));
public void Transform_WithTaperMatrix <TPixel>(TestImageProvider <TPixel> provider, TaperSide taperSide, TaperCorner taperCorner)
where TPixel : struct, IPixel <TPixel>
{
using (Image <TPixel> image = provider.GetImage())
{
Matrix4x4 m = ProjectiveTransformHelper.CreateTaperMatrix(image.Size(), taperSide, taperCorner, .5F);
image.Mutate(i => { i.Transform(m); });
FormattableString testOutputDetails = $"{taperSide}-{taperCorner}";
image.DebugSave(provider, testOutputDetails);
image.CompareFirstFrameToReferenceOutput(TolerantComparer, provider, testOutputDetails);
}
}
/// <summary>
/// Creates a matrix that performs a tapering projective transform.
/// <see href="https://docs.microsoft.com/en-us/xamarin/xamarin-forms/user-interface/graphics/skiasharp/transforms/non-affine"/>
/// </summary>
/// <param name="size">The rectangular size of the image being transformed.</param>
/// <param name="side">An enumeration that indicates the side of the rectangle that tapers.</param>
/// <param name="corner">An enumeration that indicates on which corners to taper the rectangle.</param>
/// <param name="fraction">The amount to taper.</param>
/// <returns>The <see cref="Matrix4x4"/></returns>
public static Matrix4x4 CreateTaperMatrix(Size size, TaperSide side, TaperCorner corner, float fraction)
{
Matrix4x4 matrix = Matrix4x4.Identity;
switch (side)
{
case TaperSide.Left:
matrix.M11 = fraction;
matrix.M22 = fraction;
matrix.M13 = (fraction - 1) / size.Width;
switch (corner)
{
case TaperCorner.RightOrBottom:
break;
case TaperCorner.LeftOrTop:
matrix.M12 = size.Height * matrix.M13;
matrix.M32 = size.Height * (1 - fraction);
break;
case TaperCorner.Both:
matrix.M12 = size.Height * .5F * matrix.M13;
matrix.M32 = size.Height * (1 - fraction) / 2;
break;
}
break;
case TaperSide.Top:
matrix.M11 = fraction;
matrix.M22 = fraction;
matrix.M23 = (fraction - 1) / size.Height;
switch (corner)
{
case TaperCorner.RightOrBottom:
break;
case TaperCorner.LeftOrTop:
matrix.M21 = size.Width * matrix.M23;
matrix.M31 = size.Width * (1 - fraction);
break;
case TaperCorner.Both:
matrix.M21 = size.Width * .5F * matrix.M23;
matrix.M31 = size.Width * (1 - fraction) / 2;
break;
}
break;
case TaperSide.Right:
matrix.M11 = 1 / fraction;
matrix.M13 = (1 - fraction) / (size.Width * fraction);
switch (corner)
{
case TaperCorner.RightOrBottom:
break;
case TaperCorner.LeftOrTop:
matrix.M12 = size.Height * matrix.M13;
break;
case TaperCorner.Both:
matrix.M12 = size.Height * .5F * matrix.M13;
break;
}
break;
case TaperSide.Bottom:
matrix.M22 = 1 / fraction;
matrix.M23 = (1 - fraction) / (size.Height * fraction);
switch (corner)
{
case TaperCorner.RightOrBottom:
break;
case TaperCorner.LeftOrTop:
matrix.M21 = size.Width * matrix.M23;
break;
case TaperCorner.Both:
matrix.M21 = size.Width * .5F * matrix.M23;
break;
}
break;
}
return(matrix);
}
public static SKMatrix Make(SKSize size, TaperSide taperSide, TaperCorner taperCorner, float taperFraction)
{
var matrix = SKMatrix.MakeIdentity();
switch (taperSide)
{
case TaperSide.Left:
matrix.ScaleX = taperFraction;
matrix.ScaleY = taperFraction;
matrix.Persp0 = (taperFraction - 1) / size.Width;
switch (taperCorner)
{
case TaperCorner.RightOrBottom:
break;
case TaperCorner.LeftOrTop:
matrix.SkewY = size.Height * matrix.Persp0;
matrix.TransY = size.Height * (1 - taperFraction);
break;
case TaperCorner.Both:
matrix.SkewY = (size.Height / 2) * matrix.Persp0;
matrix.TransY = size.Height * (1 - taperFraction) / 2;
break;
}
break;
case TaperSide.Top:
matrix.ScaleX = taperFraction;
matrix.ScaleY = taperFraction;
matrix.Persp1 = (taperFraction - 1) / size.Height;
switch (taperCorner)
{
case TaperCorner.RightOrBottom:
break;
case TaperCorner.LeftOrTop:
matrix.SkewX = size.Width * matrix.Persp1;
matrix.TransX = size.Width * (1 - taperFraction);
break;
case TaperCorner.Both:
matrix.SkewX = (size.Width / 2) * matrix.Persp1;
matrix.TransX = size.Width * (1 - taperFraction) / 2;
break;
}
break;
case TaperSide.Right:
matrix.ScaleX = 1 / taperFraction;
matrix.Persp0 = (1 - taperFraction) / (size.Width * taperFraction);
switch (taperCorner)
{
case TaperCorner.RightOrBottom:
break;
case TaperCorner.LeftOrTop:
matrix.SkewY = size.Height * matrix.Persp0;
break;
case TaperCorner.Both:
matrix.SkewY = (size.Height / 2) * matrix.Persp0;
break;
}
break;
case TaperSide.Bottom:
matrix.ScaleY = 1 / taperFraction;
matrix.Persp1 = (1 - taperFraction) / (size.Height * taperFraction);
switch (taperCorner)
{
case TaperCorner.RightOrBottom:
break;
case TaperCorner.LeftOrTop:
matrix.SkewX = size.Width * matrix.Persp1;
break;
case TaperCorner.Both:
matrix.SkewX = (size.Width / 2) * matrix.Persp1;
break;
}
break;
}
return(matrix);
}
/// <summary>
/// Creates a matrix that performs a tapering projective transform.
/// <see href="https://docs.microsoft.com/en-us/xamarin/xamarin-forms/user-interface/graphics/skiasharp/transforms/non-affine"/>
/// </summary>
/// <param name="size">The rectangular size of the image being transformed.</param>
/// <param name="taperSide">An enumeration that indicates the side of the rectangle that tapers.</param>
/// <param name="taperCorner">An enumeration that indicates on which corners to taper the rectangle.</param>
/// <param name="taperFraction">The amount to taper.</param>
/// <returns>The <see cref="Matrix4x4"/></returns>
public static Matrix4x4 CreateTaperMatrix(Size size, TaperSide taperSide, TaperCorner taperCorner, float taperFraction)
{
Matrix4x4 matrix = Matrix4x4.Identity;
switch (taperSide)
{
case TaperSide.Left:
matrix.M11 = taperFraction;
matrix.M22 = taperFraction;
matrix.M13 = (taperFraction - 1) / size.Width;
switch (taperCorner)
{
case TaperCorner.RightOrBottom:
break;
case TaperCorner.LeftOrTop:
matrix.M12 = size.Height * matrix.M13;
matrix.M32 = size.Height * (1 - taperFraction);
break;
case TaperCorner.Both:
matrix.M12 = (size.Height * 0.5f) * matrix.M13;
matrix.M32 = size.Height * (1 - taperFraction) / 2;
break;
}
break;
case TaperSide.Top:
matrix.M11 = taperFraction;
matrix.M22 = taperFraction;
matrix.M23 = (taperFraction - 1) / size.Height;
switch (taperCorner)
{
case TaperCorner.RightOrBottom:
break;
case TaperCorner.LeftOrTop:
matrix.M21 = size.Width * matrix.M23;
matrix.M31 = size.Width * (1 - taperFraction);
break;
case TaperCorner.Both:
matrix.M21 = (size.Width * 0.5f) * matrix.M23;
matrix.M31 = size.Width * (1 - taperFraction) / 2;
break;
}
break;
case TaperSide.Right:
matrix.M11 = 1 / taperFraction;
matrix.M13 = (1 - taperFraction) / (size.Width * taperFraction);
switch (taperCorner)
{
case TaperCorner.RightOrBottom:
break;
case TaperCorner.LeftOrTop:
matrix.M12 = size.Height * matrix.M13;
break;
case TaperCorner.Both:
matrix.M12 = (size.Height * 0.5f) * matrix.M13;
break;
}
break;
case TaperSide.Bottom:
matrix.M22 = 1 / taperFraction;
matrix.M23 = (1 - taperFraction) / (size.Height * taperFraction);
switch (taperCorner)
{
case TaperCorner.RightOrBottom:
break;
case TaperCorner.LeftOrTop:
matrix.M21 = size.Width * matrix.M23;
break;
case TaperCorner.Both:
matrix.M21 = (size.Width * 0.5f) * matrix.M23;
break;
}
break;
}
return(matrix);
}