Fading an Image Away

• Download demo - 7.8 KB

Introduction

While working on my new project (chronology control), I needed the ability to differentiate between more and less important parts of data. My idea was to put more important parts of data to the center of screen and have less important parts fade away.

Using double buffering, I would draw the visible part of the control to bitmap and then fade it proportional to the distance from the center.

Surprisingly enough, I didn't find a quick and simple solution to the problem of gradually fading away the bitmap, anywhere on the net. Thus disregarding the danger of my short-n-cute article being stigmatized as "yet another LinearGradientBrush derivate", I decided to share this neat trick with you.

How to Fade an Image Away

The solution to this problem is painting a simple transparent gradient over the image. I use linear gradient in the demo, but you could use path gradient to achieve more spectacular results. This gradient must progress from completely transparent black color - this will give the important part of your picture less vague appearance with natural colors - towards less transparent color of the background.

Technically, from alpha 0 and RGB(0,0,0) to alpha 255 and the background color.

The following code does it all:

// Preconditions: image, graphics and backColor initialized
Rectangle imageRect=new Rectangle(0,0,image.Width,image.Height);
// Place it on the window.
graphics.DrawImage(image,imageRect);
// Create gradient brush from black to window's back color.
LinearGradientBrush brush=new
LinearGradientBrush(new Rectangle(0,0,image.Width,image.Height),
    Color.FromArgb(0,0,0,0),
    backColor,
    0,false);
// And paint it over image...
e.Graphics.FillRectangle(brush,imageRect);
// ...voila!

History

• 13^th October, 2003: Initial version