Wrong value in getting pixel value from SharpDX.Diret2D1.Bitmap1

hoahong · 2019-08-07T06:41:08

Hi guys, I created a Bitmap1 and filled it with RawColor4(1f, 0.0f, 0.0f, 0.5f) by this code: D2D1.Bitmap1 img = new D2D1.Bitmap1(_graphics.D2D1Context5, new SharpDX.Size2(640, 480), new BitmapProperties1() { PixelFormat = new D2D1.PixelFormat(Format.R8G8B8A8_UNorm, D2D1.AlphaMode.Premultiplied), DpiX = 96, DpiY = 96, BitmapOptions = BitmapOptions.Target }); _graphics.D2D1Context5.Target = img; _graphics.D2D1Context5.BeginDraw(); _graphics.D2D1Context5.AntialiasMode = AntialiasMode.Aliased; //RawColor4 with Red=1f; G=0.0f; B=0.0f; Alpha = 0.5f; SolidColorBrush br = new SolidColorBrush(_graphics.D2D1Context5, new SharpDX.Mathematics.Interop.RawColor4(1f, 0.0f, 0.0f, 0.5f)); _graphics.D2D1Context5.FillRoundedRectangle(new RoundedRectangle() { RadiusX = 20, RadiusY = 20, Rect = new SharpDX.Mathematics.Interop.RawRectangleF(10, 10, 630, 470) }, br); br.Dispose(); _graphics.D2D1Context5.EndDraw(); Then i use this function to get Pixel value from img above: private static Color4 GetPixel( Bitmap1 created_with_BitmapOption_Target, int x, int y) { var img1 = new D2D1.Bitmap1(_graphics.D2D1Context5, new SharpDX.Size2(created_with_BitmapOption_Target.PixelSize.Width, created_with_BitmapOption_Target.PixelSize.Height), new BitmapProperties1() { PixelFormat = new D2D1.PixelFormat(Format.R8G8B8A8_UNorm, D2D1.AlphaMode.Premultiplied), DpiX = 96, DpiY = 96, BitmapOptions = BitmapOptions.CannotDraw | BitmapOptions.CpuRead }); img1.CopyFromBitmap(created_with_BitmapOption_Target); var map = img1.Map(MapOptions.Read); var size = created_with_BitmapOption_Target.PixelSize.Width * created_with_BitmapOption_Target.PixelSize.Height * 4; byte[] bytes = new byte[size]; Marshal.Copy(map.DataPointer, bytes, 0, size); img1.Unmap(); img1.Dispose(); var position = (y * created_with_BitmapOption_Target.PixelSize.Width + x) * 4; return new Color4(bytes[position], bytes[position + 1], bytes[position + 2], bytes[position + 3]); } Then i get pixel value : Color4 c4val = GetPixel(img,50, 50); I get c4value is: Alpha=127; Red=127; Green=0; Blue=0 This color is not the same the color i filled img (Red=1f; G=0.0f; B=0.0f; Alpha = 0.5f;) Can anybody help where i was wrong in code? Thank you so much in advance, HoaHong