Joe Maller: Joe's Debug and Explore Filters: Joe's 3x3 Convolve Matrix Tester

descriptive blurb, should be one line, meant to get serach engines.

This filter is basically identical to the Quicktime Effect except that it breaks the rows into couplets of three instead of just labeling them cells 1-9. Other than that cosmetic change, they are basically identical.

 

I don't understand Matrix convolutions very well. Something I've noticed are that the total value should equal zero if you want to preserve the luminosity of the source image.

the basic idea seems to be that a pixel and the 8 pixels around it are processed by adjusting their brightness relative to the values described by the matrix. I'm not clear whether or not it is every pixel that is processed or every matrix of 9 pixels.


Photoshop's manual had some more information regarding the custom filter, which is a basic convolution filter. This said, "each pixel is reassigned a value based on the values of surrounding pixelsthat each pixel." Ok, I figured that much out pretty quickly. "This operation is similar to the Add and Subtract calculations for channels." That actually explains quite a bit.

Any pixel subtracted from itself will equal zero. However adding pixels of differing values to themselves will increase the overall intensity of the resulting pixel unitl it maxes out to white.

 

I guess it's pretty obvious that the calculations are performed on the origial image t

What is the Matrix

Matrixes have been used for image processing for a long time. Some common matrixes even have names, try these:

Sobel

Edge Detection
High Pass

PiP Convolution Kernal Examples

Custom (Photoshop) Lets you design your own filter effect. With the Custom filter, you can change the brightness values of each pixel in the image according to a predefined mathematical operation known as convolution. Each pixel is reassigned a value based on the values of surrounding pixels. This operation is similar to the Add and Subtract calculations for channels. You can save the custom filters you create and use them with other Photoshop images.

Once you start to understand the basics, this stuff soesn't look so bad anymore.

For some basic matrixes scroll to the bottom of this page.

Source Code

Unlocked versions of this and all of Joe's Debugging and Exploration Filters are included for free with the trial and paid versions of Joe's Filters. Or use the source code below to build your own.

 
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