you can read here about Gaussian blur in this wiki article.
one basic blurring consist in adding to the rgb values of a pixel, all rgb values of the pixels surrounding it.
another article explaining it well, and its implementation in Visual Basic on CodeProject.
the problem - for me - is the speed. this method is slow. so after a second thought, why treating pixel by pixel? let's try blurring the hole image at the same time.
Here is what i came up with :
Sub BlurBitmap(ByRef image As Bitmap, Optional ByVal BlurForce As Integer = 1) 'We get a graphics object from the image Dim g As Graphics = Graphics.FromImage(image) 'declare an ImageAttributes to use it when drawing Dim att As New ImageAttributes 'declare a ColorMatrix Dim m As New ColorMatrix ' set Matrix33 to 0.5, which represents the opacity. so the drawing will be semi-trasparent. m.Matrix33 = 0.5F 'Setting this ColorMatrix to the ImageAttributes. att.SetColorMatrix(m) 'drawing the image on it self, but not in the same coordinates, in a way that every pixel will be drawn on the pixels arround it. For x = -BlurForce To BlurForce For y = -BlurForce To BlurForce 'Drawing image on it self using out ImageAttributes to draw it semi-transparent. g.DrawImage(image, New Rectangle(x, y, image.Width, image.Height), 0, 0, image.Width, image.Height, GraphicsUnit.Pixel, att) Next Next 'disposing ImageAttributes and Graphics. the effect is then applied. att.Dispose() g.Dispose() End Sub
I find this way faster than treating a it pixel per pixel. try changing the value of BlurForce (which should be an integer > 0) and check the effect. have fun with it!
Any comments are very welcome.