If you want to create a uniform color instead of a transparent one it should be easy to modify (e.g. The function skips the call to the system's MakeTransparent function and directly sets the alpha channel of each pixel to 0. To the new function: ModifyHue hueChanger = new ModifyHue(MakeTransparent) Īnd call it with a suitable threshold, maybe 10 or 20.: c = hueChanger(c, 20)

You could use it in a double loop over the pixels, but for fast results you should call it from the code in this post (second part!) which uses LockBits.Ĭhange this ModifyHue hueChanger = new ModifyHue(MaxChannel)

Return val < threshold ? Color.FromArgb(0, c.R, c.G, c.B) : c This will do the job: public Color MakeTransparent(Color c, int threshold)īyte val = (byte)((c.R * 0.299f + c.G * 0.587f + c.B * 0.114f)) The example image has a back ground that needs to be removed but the colorful points on the image need to be kept without any changes. I want to have a transparent background for 'tempImage' before any points are drawn on it. G.DrawImage(tempImage, new (x_position, y_position)) But, the image still have a foggy covering on the image. my understanding about g.DrawImage() is to draw points on tempImage

But, if I uncomment it, I will have an image with black background. G.Clear(Color.Transparent) // this only give me an empty image without any points on it. tempImage = myDrawImageFunction(myPoints) Graphics g = Graphics.FromImage(canvasImage) More update of C# code to draw an image : canvasImage = new (xSize, ySize, .Format32bppArgb) ĬanvasImage.MakeTransparent(Color.Black) Gr.DrawImage(img, new Rectangle(0, 0, img.Width, img.Height),Ġ, 0, img.Width, img.Height, GraphicsUnit.Pixel, imageAttribute ) ImageAttribute.SetGamma(0.5f, ColorAdjustType.Bitmap) I used the code: ImageAttribute imageAttribute = new ImageAttribute() How to remove white background color from Bitmap Bitmap capcha = new the background still have a gray color like a fog covering the points on the image. The canvas is black and I just need to change the canvas to be transparent meanwhile keeping colorful points on it without any changes. It is just like that I draw some points on a canvas. I need to remove the black background color of a bitmap in C# VS2013.

Inkscape trace bitmap not working 2017