Difference between revisions of "GIMP"

Revision as of 09:45, 31 May 2020

GIMP is a full featured graphic / image / photo editing software set of programs and tools similar in use or functionality to Adobe Photoshop. GIMP (GNU Image Manipulation Program) is extensive enough that its own wiki page can be devoted to the software tools.

Gimp / GIMP (technically all upper case) will provide for you nearly all of the features and tools available in the expensive commercial software package Adobe Photoshop with the exception that GIMP is absolutely free. Also, unlike Adobe Photoshop, GIMP is cross-platform and open source. You can run GIMP under Linux, Windows, and MacOS. Many Linux distributions include GIMP as a part of their desktop operating systems, including Fedora and Debian.

Tools used to perform image editing can be accessed via the toolbox, through menus and dialogue windows. They include filters and brushes, as well as transformation, selection, layer and masking tools.

GIMP uses an interface made up of multiple independent windows, which can be confusing for some users. You can toggle between the default multi-window mode and the new single-window mode in GIMP 2.8 and newer through the Single-window mode checkbox in the Windows menu. In single-window mode, GIMP will put dockable dialogs and images in a single, tabbed image window. The default windows were: Toolbox (left), Main Image (middle), Layers and Brushes (right). In single window mode all three are contained within the Main Image window, which is more consistent with the user experience of Microsoft Windows software.

Customize

• CLICK Windows -> Single Window Mode (you will see a check symbol next to the label once selected)

Usage Help

Gimp works differently than other popular image manipulation software. This is because linux developers can be snobs rather than accommodating. Yes, it hurts linux, but because they think their way is best, we have to learn their way, even if it takes more time and mouse clicks.

• HOWTO: STRAIGHT LINE --- You can use pencil, paintbrush, eraser, airbrush, etc: Click and create a single dot -> hold down and maintain shift -> move to direct line -> click to complete line.

• HOWTO: ROTATE LAYER DEGREES --- Arbitrary Rotation: You can access this command from the image menubar through Layer → Transform → Arbitrary Rotation, or by using the keyboard shortcut Shift+R. THEN you might have to: Layer -> Transparency -> Remove Alpha Channel (if you're working with a simple 1 layer image and you want to restore the background.)

• HOWTO: CHANGE COLOR DEPTH --- Color Depth to 1-bit BW: Image -> Mode -> Indexed -> choose "Use black and white 1-bit palette)

• HOWTO: MOVE ACTIVE LAYER IMAGE ONLY --- Moving TEXT or an IMAGE layer: when I attempt to move text or an image in the active layer, gimp either moves the wrong layer or background layer, very stupid and annoying. SOLUTION: Hold SHIFT KEY while using the MOVE TOOL which forces Gimp to work with the current selected layer.

• HOWTO: MOVE SELECTION ONLY --- I select part of an image and when I use the move tool, it moves all of the layer. #$%! SOLUTION: Right click your selection and in the menu, select "Select -> Float." Ctrl+Shift+L Also, this makes it a temporary floating layer, so when you place it, you have to use the layers interface and "Anchor Layer" when done.

• HOWTO: REPLACE COLOR WITH ANOTHER --- In Paint Shop Pro you could select a color with the dropper and exchange it with another. With Gimp it is called the Color Exchange Function. Goto the Menu Colors -> Map -> Color Exchange and then either select the color from the preview picture using the color picker tool or just define the color to replace and the new color manually. Bug: If you have an alpha transparency you will see two tone gray squares to represent the transparency. Gimp color exchange lets you select them as if they were actual RGB colors in the image, which can be confusing, and is a programming oversight by the gimp developers as it should treat the squares as no color.

• HOWTO: COPY SELECT, PAST INTO IMAGE AND MOVE TO POSITION --- Use selection tool and create a selection. Press CTRL-C to copy then CTRL-V to paste. Choose the MOVE tool and make sure the MOVE tool is set to MOVE LAYER with Pick a Layer or Guide. Those are under the Tool Options which you should see in an area of the interface on the left center of the screen. Using the move tool you should not be able to move and place the pasted selection. After it is placed you can click anywhere outside of the selection to anchor it down, or CTRL-V again to get another copy of the selection to move and place. Basically, the extra step that PSP users aren't accustomed to involves switching to the MOVE TOOL after pasting.

• HOWTO: EDIT PALETTE IN AN INDEXED IMAGE --- use the Colormap dialog. Upper right of the interface is the dockable dialogs where you will see small tabs each to a dockable dialog. One of the dockable dialogs is Colormap, the tab symbol being four squares of colors. If the dockable dialog is not present goto WINDOWS -> DOCKABLE DIALOGS -> colormap. In the colormap dockable dialog click the color square to edit the color in the palette of the indexed image.

Anti-Aliasing

Anti-aliasing is a feature used to render smoother textures to otherwise jagged edges of an object by sampling pixels and overlapping colors from adjacent pixels, thereby rendering a smoother texture to the object. This is commonly the default for tools such as the Text Tool in The Gimp. In the Text Tool the common user typically wants this feature enabled. That's fine, and expected. However, when selecting an area of the image to crop, it is not typical to have anti-aliasing enabled.

Anti-Aliasing on the Selection Tools: The surge of Gimp, why the hell do the devs enable this PITA feature by default? For example, when you make a selection with the Ellipse Select Tool, anti aliasing is enabled by default. You won't notice it until later when you see a scum around the part of the image you cropped away and tried to fill with another color. Good grief! This is something most people would NOT want by default. You can tell devs are not application users.

Selection Tools

The four selection tools each have their own checkbox for anti-aliasing. You have to manually uncheck it for each tool prior to making the selection. If you noticed it too late, and try to use the UNDO tool then recrop with the same selection the software will not disable anti-aliasing even if you have it unchecked, another blunder by the Gimp devs.

Image Scaling

To be able to rotate, deform or scale a floating selection with the corresponding tools we have to set Interpolation to None in the Tool Options to avoid anti-aliasing.

Brush Tools

The Paintbrush Tool "P" will have anti-aliasing enabled and only the brush hardness can have any impact on this. When using the Pencil Tool "N" you can use a brush with no alpha channel.

Support

Paint Shop Pro import plugin

This plugin is crap. It fails to import traditional Jasc PSP files. It might be fine for doing a specific PSP format from the Corel days.

Gimp will not open Paint Shop Pro PSP files and with the plugin it still probably won't open your PSP file.

Workaround: For Linux perhaps the most dynamic and best available tool for this is called XnView and seems to be able to open practically any graphic file format out there with very few exceptions.