Pixel interact mode

Selects how 2 pixels interact with each other when you copy and paste parts of an image, read an image from disk, or add graphical elements.

Overwrite - Default mode. The new pixel erases the old pixel. This is by far the fastest mode.

Maximum - The larger of the 2 values is used.

Minimum - The smaller of the 2 values is used.

Add - The 2 values are added (up to the maximum value).

Subtract - The new value is subtracted from the old value (with a minimum result of 0).

XOR - The 2 values are XOR'd with each other.

Average - The 2 values are averaged.

Superimpose - The new pixel replaces the old pixel unless the new pixel's value is 0, in which case the old pixel is unaffected (allows superimposing images with parts ``masked out'').

Example 1. Finding subtle differences between two images (also creates a silhouette effect).

1. Load an image into imal.
2. Select ``Pixel interaction mode...Subtract''.
3. Select ``Open image'' and change ``x position'' and ``y position'' to 2.
4. Click on ``OK''.
5. The images have now been subtracted. (It may be necessary to make it lighter or increase the contrast.)

Example 2. Creating contour maps of an image.

1. Load an image into imal.
2. Select ``Pixel interaction mode...XOR''.
3. Select `copy', and click-and-drag to select a portion of the image.
4. Release the mouse button.
5. Move the mouse to a location 1 pixel to the right and 1 pixel below the original position and click the mouse button to put the copy in place.
6. You now have a crude contour plot of your image. The gradient sensitivity of the contour plot can be decreased by using an offset of 2 or more pixels in step (5). You can also ``threshold'' the plot by subtracting a value (``make darker'') and then adding it back(``make lighter'').

Example 3. Reducing chunkiness in image.

1. Read an image into imal.
2. Select ``Pixel interaction mode...Average''.
3. Select ``Open image'' and change ``x position'' and ``y position'' to 2.
4. Click on ``OK''.
5. You now have an image that is smoother without becoming blurred.

Don't forget to change ``Pixel interact mode'' back to ``Overwrite'' afterwards.

NOTE: Don't forget that, when loading an image, unless the interact mode is ``overwrite'', the image will interact not only with other images but also with the background in areas where no image is present. Thus it may be helpful to set the background color to black first, to avoid unexpected results.