protected override void OnPaintSurface(SKPaintGLSurfaceEventArgs args)
{
base.OnPaintSurface(args);
SKSize info = CanvasSize;
SKCanvas canvas = args.Surface.Canvas;
if (rectInfo.Width != info.Width || rectInfo.Height != info.Height)
{
rectInfo = new SKRect(0, 0, info.Width, info.Height);
SetMainBitmapMatrix();
SetTrashRects();
}
var rectImage = SkiaHelper.CalculateRectangle(rectInfo, outImageWidht, outImageHeight).rect;
OnPaintSurface(canvas, rectImage, false);
canvas.DrawSurrounding(rectInfo, rectImage, SkiaHelper.backgroundColor);
DrawTrasRect(canvas);
}
protected override void OnPaintSurface(SKPaintSurfaceEventArgs args)
{
base.OnPaintSurface(args);
SKImageInfo info = args.Info;
SKSurface surface = args.Surface;
SKCanvas canvas = surface.Canvas;
canvas.Clear(SkiaHelper.backgroundColor);
// 计算显示位图的矩形
var rect = SkiaHelper.CalculateRectangle(new SKRect(0, 0, info.Width, info.Height), bitmap);
canvas.DrawBitmap(bitmap, rect.rect);
// 计算用于显示裁剪矩形的矩阵变换
SKMatrix bitmapScaleMatrix = SKMatrix.CreateIdentity();
SKMatrix.CreateScaleTranslation(rect.scaleX, rect.scaleX, rect.rect.Left, rect.rect.Top);
// 显示矩形
SKRect scaledCropRect = bitmapScaleMatrix.MapRect(croppingRect.Rect);
using (SKPaint edgeStroke = new SKPaint())
{
edgeStroke.Style = SKPaintStyle.Stroke;
edgeStroke.Color = SKColors.White;
edgeStroke.StrokeWidth = 3;
edgeStroke.IsAntialias = true;
canvas.DrawRect(scaledCropRect, edgeStroke);
}
canvas.DrawSurrounding(rect.rect, scaledCropRect, SKColors.Gray.WithAlpha(190));
// Display heavier corners
using (SKPaint cornerStroke = new SKPaint())
using (SKPath path = new SKPath())
{
cornerStroke.Style = SKPaintStyle.Stroke;
cornerStroke.Color = SKColors.White;
cornerStroke.StrokeWidth = 7;
path.MoveTo(scaledCropRect.Left, scaledCropRect.Top + corner);
path.LineTo(scaledCropRect.Left, scaledCropRect.Top);
path.LineTo(scaledCropRect.Left + corner, scaledCropRect.Top);
path.MoveTo(scaledCropRect.Right - corner, scaledCropRect.Top);
path.LineTo(scaledCropRect.Right, scaledCropRect.Top);
path.LineTo(scaledCropRect.Right, scaledCropRect.Top + corner);
path.MoveTo(scaledCropRect.Right, scaledCropRect.Bottom - corner);
path.LineTo(scaledCropRect.Right, scaledCropRect.Bottom);
path.LineTo(scaledCropRect.Right - corner, scaledCropRect.Bottom);
path.MoveTo(scaledCropRect.Left + corner, scaledCropRect.Bottom);
path.LineTo(scaledCropRect.Left, scaledCropRect.Bottom);
path.LineTo(scaledCropRect.Left, scaledCropRect.Bottom - corner);
canvas.DrawPath(path, cornerStroke);
}
// 反转变换以进行触摸跟踪
bitmapScaleMatrix.TryInvert(out inverseBitmapMatrix);
}