![]() 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. The original tutorial can be found here (dead link).You can think of your image as a series of pixels arranged in a grid of rows and columns. Playing around with the spacing options in the brush selection dialog, the color or using one of the animated brushes you can get very interesting results. Using a fuzzy brush and selecting a blue color here is the result for the selection made above. When all the options are selected you can finally click on OK. If you select Stroke Using a Paint Tool, you will be able to use the brush that you have selected. You will get a dialog allowing you to set many options for stroking your selection, including dashed lines and other fancy features. ![]() When all the options are selected you can click on Edit -> Stroke. Choose also a color and you can play with the spacing option for the brush. Step 3 ¶Īfter you have the selection, choose a brush from the brush selection dialog. Use the selection tools to create a selection with the desired shape. When using the tools, holding shift at the beggining of the selection process will add the selection to what is already selected, while holding the control key will substract from it. There are several ways to make a selection, including all the tools in red shown above and select by color as explained on Selecting and removing one color. Step 1 ¶īefore doing that however we need to make a selection with the shape we want. This option can be accesed on the image menu (right button click on the image), by going to Edit -> Stroke Selection. The solution is to use the selection stroking capabilities of GIMP. However this doesn’t mean you can’t paint them, in fact there are some interesting options regarding this subject when it comes to GIMP. ![]() Since GIMP is an image manipulation program and not a painting program it doesn’t include tools to draw shapes like squares and circles. Text and images Copyright (C) 2002 Francisco Bustamante Hempe and may not be used without permission of the author. ![]()
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