1.1 Current Situation about GIMP Plugin Registry

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1 1.0 Introduction One of the nicest things about GIMP is how easily its functionality can be extended, by using plugins. GIMP plugins are external programs that run under the control of the main GIMP application and interact with it very closely. Plug-ins are software components that add functionality to GIMP. Plugins can manipulate images in almost any way that users can. Their advantage is that it is much easier to add a capability to GIMP by writing a small plugin than by modifying the huge mass of complex code that makes up the GIMP core. Many valuable plugins have C source code that only comes to lines or so. Several dozen plugins are included in the main GIMP distribution, and installed automatically along with GIMP. Most of them can be accessed through the Filters menu (in fact, everything in that menu is a plugin), but a number are located in other menus. In many cases you can use one without ever realizing that it is a plugin. In addition to the plugins included with GIMP, many more are available on the Internet. A large number can be found at the GIMP Plugin Registry ( a web site whose purpose is to provide a central repository for plugins. Creators of plugins can upload them there; users in search of plugins for a specific purpose can search the site in a variety of ways. Anybody in the world can write a GIMP plugin and make it available over the web, either via the Registry or a personal web site, and many very valuable plugins can be obtained in this way. Some plug-ins have been thoroughly tested, while others have not. 1.1 Current Situation about GIMP Plugin Registry By the end of June 2018 the Plugin Registry registry.gimp.org was completely down. In fact, starting from mid of 2015 onward, the Plugin Registry had not been performed any new updated at all. The whole website became static and in read only mode. The only possibility was to download the plug-ins if you had the direct link provided; now it indeed become completely down. Fortunately, there is a copy of the whole website at the address of for you to be able to download this plug-ins again as a compressed file of size around 150 Mbyte! One more thing that you need to take notice of is that new version of Gimp has been released: version 2.10 since end of April However, this 2.10 version doesn't work well with the plugins that you have installed in the 2.8 version. If you install Gimp 2.10, you will get several error messages, and several plugins (Save for Web, Layer via Copy, the Photoshop CS6 theme) will not be working anymore. Compiled by K.T. NG Sept. 2018, Rev 1.0 Page 1

2 1.2 Installing Plug-ins When you decide that you want to use a plug-in from the registry, you have to download it and install it so GIMP can recognize it. For most plug-ins, this is a fairly straightforward process. To be safe, though, if the plug-in includes a README file or any sort of installation instructions, it's highly recommended that you read through them and do what they suggest. When it comes to plug-ins, you'll encounter two main types: scripts and plug-ins. When writing programs, developers can write in all sorts of programming languages. These languages can be split into two main categories: scripting languages and compiled languages. GIMP natively supports the Python (with the.py file extension), Perl, and Scheme (with the.scm file extension) scripting languages. GIMP itself is written in a compiled language called C. Note: A GIMP script written in Scheme is referred to as a Script-Fu. Although the GIMP Plugin Registry and even some GIMP documentation use the term "plug-in" as a generic term, for configuration and installation purposes a plug-in written in a scripting language is called a script, and a plug-in written in a compiled language is actually a plug-in. Installing Scripts Of the two types of plug-ins, scripts are the simplest to install. If you download them from the registry, they should be pretty easy to pick out. The script file usually has a.scm extension at the end of the filename. Installing them is as easy as copying that file to your GIMP scripts folder. To see where your scripts folder is, check your preferences (Edit > Preferences) under Folders > Scripts. The path is normally in the format of C:\Users\username\.gimp-2.8\scripts. Installing Compiled Plug-Ins This process is used for compiled plug-ins as well as plug-ins written in Python. Generally speaking, you install these plug-ins in much the same way that you would install a Script-Fu script. For simple compiled plug-ins or Python scripts, the installation process is often as easy as copying the plug-in to one of these folders and restarting GIMP. To see where your Plug-ins folder is, check your preferences (Edit > Preferences) under Folders > Plug-Ins. The path is normally in the format of C:\Users\username\.gimp-2.8\plug-ins. After copy the files into the appropriate subdirectory, you only have to restart GIMP. Most plug-ins and script after installation will appear in submenus of the Filter menu or in the new Script-Fu menu. Compiled by K.T. NG Sept. 2018, Rev 1.0 Page 2

3 2.0 A Few Plug-ins Worth Mentioning Now we know the process to install GIMP plugins. Next, it is time to get to know some cool plugins. The following sections describe some interesting plug-ins available on the GIMP Plugin Registry that can make your life easier or give you additional features that don't ship with the official version of GIMP. 2.1 Resynthesizer Plugin GIMP Resynthesizer Plugin is a kind of tool that helps you to remove unwanted objects from photos, repeat or transfer textures. Also, you can add tiles (vertically or horizontally) and heal your image seamlessly according to your preferences. After Resynthesizer Plugin has been installed in GIMP. You can now, use Resynthesizer options from Filters > Enhance, Filters > Map and Filters > Render and choose the desired functionality like Heal Selection, Heal Transparency, Uncrop, Style, texture etc. Resynthesizer includes many features into the Filter Menu > Enhance. These are: 2.2 GIMP Heal Selection Tool Heal Selection is one of the most used and popular features in this group and is indeed very useful. With the help of this tool, you can remove unwanted content, object or thing from your image. You just need to select the object or thing you want to remove from your image and Heal Selection will replace the selection to look like its surroundings. In its dialogue box, it offers you to select the Context Sampling Width (in pixels), where you can enter the number of pixels from the surrounding of the selected sample you want Heal Selection to pick and give your selection the appropriate texture. Compiled by K.T. NG Sept. 2018, Rev 1.0 Page 3

4 You can also select "Sample from" i.e. from where around your selected sample you want to source pixels. It is by default at "All around", but you can choose "Sides" and "Above and below" as well according to your preferences. I find this helpful, especially where there is a hard delineation in an image. Other than this you can also select the Filling Order of your selection. By default the order is set at random but, you can select "Inwards towards Center", "Outwards from Center". 2.3 GIMP Heal Transparency Tool The Heal Transparency is an easy to use and very handy healing tool when it comes to broken patches in the images. It is a versatile tool and very useful especially when you need to fill in the missing areas. It heals every transparent pixel in your image. Heal Transparency option by default is Grayed Out thus to use this option you need to right click on the layer and select add Alpha Channel. Once added you could use this option to heal broken patches in your image. In its dialogue box, it offers you options to adjust Context Sampling Width (in pixels) and Filling Order of your selection. Compiled by K.T. NG Sept. 2018, Rev 1.0 Page 4

5 Before After 2.4 GIMP Enlarge and Sharpen Tool Enlarge and Sharpen as the name suggests is a functionality to Enlarge and Sharpen your image. GIMP Sharpen function gathers information from the surrounding pixels and increases contrast where some contrast already exists. Compiled by K.T. NG Sept. 2018, Rev 1.0 Page 5

6 This function enlarges your image and sharpens it by proportion to make the image look a bit more pixelated. In its dialogue box, it offers you a functionality to adjust the amount from [1-32] to which you want to Enlarge or Sharpen your image on the Scale. 2.5 GIMP Uncrop Tool Uncrop is not exactly inverse to crop by rather a bit different. It makes the canvas larger and heals the transparent border. It is very useful when you want to expand the boundaries of your image. It works best for small enlargement of natural edges. Uncrop enlarges the image by matching the border of the image to the edge maintaining the appropriate perspective. In its dialogue box, you can adjust the Percentage of Enlargement of your image. 2.6 GIMP Sharpen by Synthesis Tool This feature is used to sharpen images by synthesizing them. It could be considered as a more realistic variant of sharpening providing the image some clear details. Compiled by K.T. NG Sept. 2018, Rev 1.0 Page 6

7 In its dialogue box, you can adjust the amount you want to sharpen your image by Synthesis. Now, apart from these features in Filter > Enhance, GIMP Resynthesizer plugin offers some other features as well. In Filter > Map it adds two very handy features Resynthesizer and Style and in Filter > Render it offers Texture. However, these features of being able to add texture, export texture and also makes your image tileable are only useful for web page design, thus we'll not cover in here. 3.0 Liquid Rescale GIMP Plugin Whenever you scale an image, all of the objects within the image scale accordingly. With the Content-Aware Resizing feature, you can scale the entire image and the key elements don't scale, just the space between them. One of the GIMP Plug-In called "Liquid Rescale" has acquired such a content-aware resizing feature aims at resizing pictures non uniformly while avoiding distortion of the important parts. Compiled by K.T. NG Sept. 2018, Rev 1.0 Page 7

8 To see how this can be done, here you can find two simple examples of what can be obtained using this plugin. 3.1 Basic Enlarging with a Preservation Mask 1. Open the image in GIMP. Duplicate the background layer and rename it Enlarge with Preserve Mask. Then in the Gimp menu, choose Layer and then Liquid Rescale. 2. In the plugin main dialog, check the "preserve features" option under the "Feature preservation mask" section on the right and then Press the "New" button on its right. A new transparency layer will be created. And the plugin main dialog will be substituted by a small dialog. Compiled by K.T. NG Sept. 2018, Rev 1.0 Page 8

9 Note: Don't press the OK button yet. And the painting need not be highly accurate. 3. Paint on the areas of the image you want to preserve, e.g. with the paintbrush. When you're done, press OK in the small window: the main dialog will appear again. You should see your preservation mask appear in the preview 4. In the Select new width and height section on the left, change the selection from pixel to percent and set the value of the Width to 120%. 5. Go to the Output tab, check the Output on a new layer; and also check for the Output the seams; Resize image canvas options and the Resize auxiliary layers option. Then click Ok If you look at the seam map, and keep the preservation mask visible on the top, you will notice that the seams do not cross the areas which were marked for preservation (unless they are too big). This, of course, implies that the seams have to cross some other areas, and it is therefore possible that these will be affected by excessive distortion. Compiled by K.T. NG Sept. 2018, Rev 1.0 Page 9

10 6. Hide the visibility of the 2 top most layers. You'll notice that the canvas will have been resized to the new output value. The area that you had masked will have preserved its original proportions. Original Image After Liquid Rescale is Applied Compiled by K.T. NG Sept. 2018, Rev 1.0 Page 10

11 The Final Image After Liquid Rescale is Applied 3.2 Quick Element Removal The easiest way to remove an element from an image is the following: 1. Open the image in GIMP. Duplicate the background layer and rename it Element Removal. Then in the Gimp menu, choose Layer and then Liquid Rescale. 2. In the plugin main dialog, check the "Discard features" option under the "Feature discard mask" section on the right and then Press the "New" button on its right. A new transparency layer will be created. And the plugin main dialog will be Compiled by K.T. NG Sept. 2018, Rev 1.0 Page 11

12 substituted by a small dialog. 3. Choose the paint tool and paint over the area you wish to remove. When you're done, press OK in the small window: the main dialog will appear again. You should see your preservation mask appear in the preview. 4. Click the Auto size button at the bottom of the Discard features section. 5. Go to the Output tab, check the Output on a new layer; and also check for the Output the seams; Resize image canvas options and the Resize auxiliary layers option. Then click OK This procedure will only give good results with simple images and very simple discard masks. If you use the options to see the seam map like described above, you will notice that the seams this time will tend to cross the areas which you marked for removal, therefore deleting them. Compiled by K.T. NG Sept. 2018, Rev 1.0 Page 12

13 6. Use the Eraser Tool to clean up for any defects and the final image should look like in here 4.0 What Is Dynamic Range in Photography? In photography, the "dynamic range" is the difference between the darkest and lightest tones in an image, generally pure black and pure white. Dynamic range is measured in "stops". An increase of one stop equals a doubling of the brightness level. The human eye can perceive about 20 stops of dynamic range in ideal circumstances. This means that the darkest tones we can perceive at any time are about 1,000,000 times darker than the brightest ones in the same scene. This is how you can still see details in dark shadows on a bright, sunny day. Cameras have a narrower dynamic range than the human eye, although the gap is closing. The best modern cameras like the Nikon D810 can achieve just fewer than 15 Compiled by K.T. NG Sept. 2018, Rev 1.0 Page 13

14 stops of dynamic range in any one photo. Most digital cameras get somewhere between 12 and 14. This is why when you take photos on a sunny day you often have to choose whether you "blow out your highlights", making them pure white, or "crush your shadows", making them pure black in the final image. In the photo below when the camera is chosen to expose correctly for the highlights. All the shadow detail in the bushes is basically black but the sky is blue. On the other hand, when being exposed correctly for the shadows, you can see the shadow details, but the sky is white. Unlike the human eye, a camera can't adjust for shadows and highlights in the same scene with just a single shot. One method photographers use to overcome dynamic range problems is High Dynamic Range (HDR) photography. In HDR photography, you combine multiple Compiled by K.T. NG Sept. 2018, Rev 1.0 Page 14

15 exposures to create a single final image. Below, photo is the combination of the two exposures with some HDR software. As you can see, the sky and bushes are both pretty well exposed. Typically, we shoot 3 (one image exposure for the highlights, one image to perfectly expose the mid-tones and one image to get a just right exposure for the darkest areas of our scene) or more images all at different exposures and then use powerful software to combine those images into a High Dynamic Range image. Note: Bracketing usually refers to exposure bracketing: the photographer chooses to take one picture at a given exposure, one or more brighter; and one or more darker; in order to select the most satisfactory image. 4.1 Make an HDR Photo in GIMP with the Exposure Blend This is quite a straightforward plugin to use and can produce a relatively good result, though it's not as rounded as a true HDR app. For example, you're limited to just three bracketed exposures, but this should be sufficient in most cases. In order to make an HDR photo in GIMP, you'll need to have three bracketed exposures of the same scene taken with your camera mounted on a tripod to ensure that they'll align perfectly. Go to Filters > Photography > Exposure Blend and the Exposure Blend dialog will open. As we're going to use the plugin's default settings, you only need to select your three images using the correct select field. You just need to click on the button beside the Normal Exposure label and then navigate to the specific file and click open. You Compiled by K.T. NG Sept. 2018, Rev 1.0 Page 15

16 will then need to select the Short Exposure and Long Exposure images in the same way. Once the three images are selected, just click the OK button and the Exposure Blend plugin will do its thing. Normal Dark Bright Result Compiled by K.T. NG Sept. 2018, Rev 1.0 Page 16

17 4.2 Adjust Layer Opacity to Tweak the Effect Once the plugin has finished running, you'll be left with a GIMP document that consists of three layers, two with layer masks applied that combine to produce a complete photo that covers a wide dynamic range. In HDR software, Tone Mapping would be applied to the image to strengthen the effect. That isn't an option here, but there are a couple of steps that we can take to improve the image. Often at this stage, the HDR photo can appear a little flat and lack in contrast. One way to counter this is to reduce the opacity of one or two of the upper layers in the Layers palette, to reduce the effect that they have on the combined image. In the layers palette, you can click on a layer and then adjust the Opacity slider and see how this affects the overall image. We reduced both of the upper layers by 20%, more or less. 4.3 Make Fake HDR (High Dynamic Range) effect with Gimp With this Fake HDR Effect plug-in for Gimp you can make High Dynamic Range photos with just a single shot photo. After running the script on the original photo it has a more color look and it's like it has a bit 'bump'- effect, a little 3D effect. How does it works 1. Open an image file in Gimp 2. Go to Script-Fu Menu > Enhance > Fake HDR Effect Here you can manage the Dark Layer Opacity (35 is the default value). Then Compiled by K.T. NG Sept. 2018, Rev 1.0 Page 17

18 click OK After Gimp has calculated the filter you now see a more colorful picture. Before After Compiled by K.T. NG Sept. 2018, Rev 1.0 Page 18

19 5.0 What is Panorama Photography? A panorama is usually an image with a large angle-of-view. Often, it has one side much longer than the other. Panoramic photography is a technique in which multiple images are stitched together to increase the field of view. Typical Panoramic Photos can consist of anywhere from 2 up to 5 or 6 images. 5.1 Advantages of Multiple Image Panoramas Some photographers capture panoramas as a single image using a wide angle lens, but to capture several images with a longer lens, and then stitch them together during post-processing have the following benefits: The panorama can be as wide as you want. The panorama will have higher resolution and more detail. Lens vignetting will often be minimized. 5.2 Process Overview Making a panorama photo is generally a two-step process: 1. Capture of images: Enough photographs are taken to cover the desired field of view. Images are taken carefully with some overlap between adjacent ones. 2. Stitching: Specialized software is used to create a panoramic photo from captured images. The panorama software can be fully automatic, partially automatic or mostly manual. Two additional steps may be needed for more complex panoramas. One is to mask unwanted parts of images and remove geometric distortion before the stitching process. The other is to manipulate the output to remove issues left by the stitching software. 5.3 Capturing Images for Stitching a Panorama The goal of the image capture step is to gather image which a stitching program can use to assemble a seamless panorama. Stitching images together is a rather complex operation for software to do and many potential issues can prevent a proper panorama from being generated. The more care is taken during the capture step; the more chances there are that a seamless panorama can be produced. Compiled by K.T. NG Sept. 2018, Rev 1.0 Page 19

20 5.3 Image Overlap Overlapping is one of the important areas in creating a panoramic image. The more overlap, the better. It is generally recommended to have overlapped the images by about 1/3. This means that the second picture will repeat about 1/3 of the first picture. The third picture will overlap the second picture by 1/3, etc. If you have a tripod that shows degrees, each photo should be 25 to 30 degrees apart. These overlap regions are used by panorama software to determine how to stitch images together. 5.4 Creating Panoramic Photos Using Autostitch Modern panorama software makes stitching images extremely easy. Autostitch is a wonderful invention for panoramic photography. Autostitch is obtainable as a ZIP file directly from the website. There is nothing to install as long as your computer can open ZIP files already. Simply extract the content and start the executable. To uninstall, just delete the files and you are done. The steps to use Autostitch are: 1. Run the program autostitch.exe. 2. Choose the output size from the Edit > Options menu. If unsure left everything as the default. Select Scale and 100% next to it. This will give the maximum size. Compiled by K.T. NG Sept. 2018, Rev 1.0 Page 20

21 3. Select File > Open and select a set of images to be stitched. As usual, use Ctrl-Click or Shift-Click to select multiple files. Currently, the input images must be in JPEG format. 4. There is no step 4! Autostitch will automatically align the images, taking a few seconds per image. Then it will create a panorama with the file name pano.jpg in the input directory, and open it in the default image editor. Below is an example that shows the result of stitching images before and after by using Autostitch. Image 1 Image 2 Compiled by K.T. NG Sept. 2018, Rev 1.0 Page 21

22 Image 3 Result Open the pano.jpg image in GIMP and use the crop tool to adjust its four handles to shrink the cropping frame (remove out all the black edges) to crop the final image. Final Result after Cropping Compiled by K.T. NG Sept. 2018, Rev 1.0 Page 22