绘制与GDI自定义透明度的图像+ [英] Draw an image with custom transparency in GDI+

问题描述

我抽签影像（​​所有的尺寸= 24×24像素格式= 32BppPArgb）上使用Drawing.Graphics对象和的DrawImage（）功能的控制。这是可能的缩小在我的应用程序，这意味着Graphics对象已变换矩阵连接到它控制缩放和平移。

I'm drawing lots of images (all of them dimensions=24x24 pixelformat=32BppPArgb) onto a Control using a Drawing.Graphics object and the DrawImage() function. It's possible to zoom out in my application which means that the Graphics object has a Transform Matrix attached to it which controls both zooming and panning.

有一个在当变焦低于50％绘制这些图标是没有意义的，但我想从图纸图标过渡到不绘制图标顺畅。即，起始于70％，图标应当与另外的透明度因子绘制，以便它们将变得完全透明，在50％。

There's no point in drawing these icons when the zoom drops below 50%, but I'd like to make the transition from drawing icons to not drawing icons smoother. I.e., starting at 70%, icons should be drawn with an additional transparency factor so that they will become completely transparent at 50%.

我如何可以得出一个额外的透明位图没有它采取显著长于的DrawImage（）？

How can I draw a bitmap with an additional transparency without it taking significantly longer than DrawImage()?

谢谢， 大卫

推荐答案

您只需要创建一个合适的嘉洛斯，初始化一个ImageAttributes对象与它传递ImageAttributes对象以Graphics.DrawImage的重载版本之一。此示例将会给你50％transparancy：

You just create an appropriate ColorMatrix, initialize a ImageAttributes object with it and pass that ImageAttributes object to one of the overloaded version of Graphics.DrawImage. This sample will give you 50% transparancy:

  float[][] matrixAlpha =
  {
   new float[] {1, 0, 0, 0, 0},
   new float[] {0, 1, 0, 0, 0},
   new float[] {0, 0, 1, 0, 0},
   new float[] {0, 0, 0, 0.5f, 0}, 
   new float[] {0, 0, 0, 0, 1}
  }; 
  ColorMatrix colorMatrix = new ColorMatrix( matrixAlpha );

  ImageAttributes iaAlphaBlend = new ImageAttributes();
  iaAlphaBlend.SetColorMatrix(
   colorMatrix,
   ColorMatrixFlag.Default,
   ColorAdjustType.Bitmap );

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