The filter makes an image look like an old brown photo. The main idea of the algorithm:

• transform to YIQ color space;
• modify it;
• transform back to RGB.

1) RGB -> YIQ:

Copy 

Y = 0.299 * R + 0.587 * G + 0.114 * B
I = 0.596 * R - 0.274 * G - 0.322 * B
Q = 0.212 * R - 0.523 * G + 0.311 * B

2) update:

Copy 

I = 51
Q = 0

3) YIQ -> RGB:

Copy 

R = 1.0 * Y + 0.956 * I + 0.621 * Q
G = 1.0 * Y - 0.272 * I - 0.647 * Q
B = 1.0 * Y - 1.105 * I + 1.702 * Q

The filter accepts 24/32 bpp color images for processing.

Sample usage:

CopyC#

// create filter
Sepia filter = new Sepia( );
// apply the filter
filter.ApplyInPlace( image );

Initial image:

Result image: