Image Arithmetic
Add - Example 3

The examples on this page use the same images as the previous two pages. This page illustrates various bias values used with unclipped addition and a divisor of 2. This is equivalent to using the unclipped "average" function with a divisor of 1.

Add — unclipped divisor 2 bias 40

Original #1
Original #2
Add — Unclipped d=2, bias 40

If you use bias without clipping, some colors will wrap around. At only 40 bias, this is only happening to a few pixels.

Add — unclipped divisor 2 bias 80

Original #1
Original #2
Add — Unclipped d=2, bias 40
Add — Unclipped d=2, bias 80

At 80 bias, quite a few more pixels have wrapped around.

Add — unclipped divisor 2 bias 120

Original #1
Original #2
Add — Unclipped d=2, bias 40
Add — Unclipped d=2, bias 80
Add — Unclipped d=2, bias 120
Add — Unclipped d=1, bias 0

At bias=120, the image is beginning to look very similar to the add unclipped divisor=1 bias=0 image from the first example page.

Add — unclipped divisor 2 bias -40

Original #1
Original #2
Add — Unclipped d=2, bias 40
Add — Unclipped d=2, bias 80
Add — Unclipped d=2, bias 120
Add — Unclipped d=1, bias 0
Add — Unclipped d=2, bias -40

A bias of -40 darkens the image but allows wrap-around. Only a very small amount of wrap-around occurred here.

Add — unclipped divisor 2 bias -80

Original #1
Original #2
Add — Unclipped d=2, bias 40
Add — Unclipped d=2, bias 80
Add — Unclipped d=2, bias 120
Add — Unclipped d=1, bias 0
Add — Unclipped d=2, bias -40
Add — Unclipped d=2, bias -80

A bias of -80 has much more wrap-around.