By using this particular Kernel, the source image would be shifted downward by 1 pixel. Otherwise, you may need to change the Divisor or Offset values to prevent the image from becoming too light. In GIMP, if you have the Normalize option selected, the software will do some calculations and attempt to retain the original brightness of the image. This final result becomes the new pixel value for the Evaluated Pixel at the center of the grid. Presuming our Divisor was set to 1 and the Offset was set to 0, our final result should still be 42. As a final step, the Bias or Offset value is added to the result in order to calculate new brightness values. If we add up all the values from the example above (0+42+0+0+0+0+0+0+0) the result is 42, which is then divided by the Divisor value of 1. These values are then totaled up, divided by the Divisor value, and then the Offset value is added to the result. This will give us a value of 42 (42×1=42) in the top row. (40*0) (42*1) (46*0)Īs the calculations are performed on the values surrounding the Evaluated Pixel using the example Kernel, every result will be 0 except for the upper middle box, where there is a 1. Wherever there is no value at all, or a value of 0, no operation will be performed at all, and a result of 0 will be returned for that square in the grid. Subsequently, each of the pixels surrounding the Evaluated Pixel will be multiplied by their corresponding Matrix Values in the Kernel. If we use the values from the example image above, the value of the Evaluated Pixel (50) in the source image is multiplied by the Kernel Value (0). The green box represents the area that will be affected by the Kernel, and calculations are performed starting from the top left, working over to the right before moving down to the next row of pixels, much like reading a book from line to line. We will refer to the value in the red box above as the Evaluated Pixel, and the value from the center grid as the Kernel Value.

The pixel value from the source image (left) is multiplied by the value from the corresponding square in the Kernel (center) which gives a resulting brightness value (right) The result is then divided by the Divisor and totaled with the Offset value. The grid in the center represents the Kernel that will be applied to the image, while the grid on the right represents the final calculated pixel value that is returned and applied to the image. Looking at the example above, taken directly from the GIMP documentation, the grid on the left represents the Source Image, and each of the numbers is a pixel value in that image. You can think of your image as a series of pixels arranged in a grid of rows and columns.

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