Halloween Fun - Embedding Ghosts Watermark in images with C#

For those of you who are going to celebrate Halloween on the 31st , here is a nice cool thing to do with C# and System.Drawing library.
In this post I'll show you how to use C# to embed a ghost image with a background image.

First we'll pick out the ingredients:
A ghost image


And for background I've picked a times square shot taken by barcoder96

ok, now that we have these, let's start getting our hands code dirty.
open up a console project , and add the System.Drawing reference by adding a using System.Drawing;
Next, type in the following code

Image backImg = Image.FromFile("e:/pictures/times.jpg");

Image ghostImg = Image.FromFile("e:/pictures/ghost.png");

Graphics g = Graphics.FromImage(backImg);

g.DrawImage(ghostImg, backImg.Width/2, 10);

backImg.Save("e:/pictures/halloween.jpg");

What's happening here is that we basically load up our background image and foreground image, we acquire a graphics object from the background image, and use it to paint over the foreground image. Looks simple, right ? here is the result

 

But to make it more ghost realistic (there's an oxymoron for you), we'll make the ghost more transparent

for that, I'm using an image color manipulation trick I first saw here (and there's also a good one here)
The Matrix33 value below sets the level of opacity or transparency. 0 is full transparency , 1 is no transparency at all.
The matrix multiply all of the colors with the new opacity value which "fades" out the colors and thus gives it the requires transparency.

Bitmap transparentGhost = new Bitmap(ghostImg.Width, ghostImg.Height);
Graphics transGraphics = Graphics.FromImage(transparentGhost);
ColorMatrix tranMatrix = new ColorMatrix();
tranMatrix.Matrix33 = 0.25F; //this is the transparency value, tweak this to fine tuned results.

ImageAttributes transparentAtt = new ImageAttributes();
transparentAtt.SetColorMatrix(tranMatrix, ColorMatrixFlag.Default, ColorAdjustType.Bitmap);
transGraphics.DrawImage(ghostImg, new Rectangle(0, 0, transparentGhost.Width, transparentGhost.Height), 0, 0, transparentGhost.Width, transparentGhost.Height, GraphicsUnit.Pixel, transparentAtt);
transGraphics.Dispose();

g.DrawImage(transparentGhost, backImg.Width / 2, 10);
backImg.Save("e:/pictures/halloween2.jpg");

And if you iterate it some more , and give it some skewing you can get the following result.




For achieving this , you can use the YAEL C# image manipulation library which provides a watermark image filter

Or trying this Halloween Ghosts Image filter online at http://www.imgtoys.com