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PAIE 01 - GIMP Layer Mask - Highlighting an Area of Interest in a Photograph


In this application note  a demonstration is provided, when using GIMP, on how to use the layer mask to edit an image to highlight areas of interest. In this example the method is used on a photograph of an electronics board (the 2 x 13 Way Mixed Signal Dilettante Board) to highlight some components   of importance.




In the image, seen in the Figure below, it is required to highlight some artifacts (BNC connectors, Arduino motor shield, the FT232RL USB to serial converter and a mini solderless breadboard) of interest. The photo editing in this application note has been undertaken using an Acer C7 Chromebook configured to run ChrUbuntu LINUX, running Ubuntu 12.04, with 16GB of RAM.


100001bFirstly, the image, or photograph, is opened in GIMP, which automatically imports it onto the Background Layer. Opening an image in GIMP is simply a case of right clicking, in the canvas area, then selecting File->Open from the main menu. Presumably, most photo editing applications work the same way.



Secondly, a new visible layer is created by selecting Layer -> New Visible Layer from the main menu. On this newly created layer, which is titled the visible layer in the image on the left below, the Rectangle Select Tool (or a similar select tool), found in the Toolbox, is used to create regions of interest. Multiple areas of interest can be selected by holding down the shift key when using the selection tool. 

The selected areas of interest are then used to form a layer mask by selecting Layer -> Mask -> Add Layer Mask from the main menu.  Doing so pops-up the Add Layer Mask dialogue where the Selection item is chosen as the one to intialise the mask to, as can be seen in the image, on the right, above. We now have two layers, the visible layer consisting of our mask and the background layer containing the original image,  seen on the left and right respectively, in the image below.


Once this has be done the visible layer can be switched off by clicking on the layer's eye, in the Layers, Channels dialogue. Next, with the background layer selected, the opacity of the layer can be adjusted. An opacity of between 40% and 60% tends to work well depending on the type of image being worked with. In the image on the right, above , the opacity has been set to 55%. When satisfied, with the opacity setting, the visible layer can be switched back on and the final image is created  by flattening the visible and background layers before saving. The result of performing all these steps can be seen in the final image below.



 This techmique has proven very useful in creating highlighted areas of interest in a photograph. The method was so easy that in fact it was more difficult writing this applicationn note comapred to doing it.



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