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On this page, i will post some easy but helpful tricks you can do with GIMP. It's a free downloadable program, that is very helpful in editing images. I've been using it for almost every single .png image i've uploaded since late 2011. GIMP
GIMP Troll

Everyone has a favorite image editor!

Creating Alpha channel

Color models such as RGB, HSL, and HSV have 16,581,375 different displayable colors (!!!). Alpha Channel, if added, gives the ability to add opacity to images, which is quite helpful if you don't want a background for your image, or would like to paste this image later above another image.

You can add Alpha Channel by right-clicking anywhere in your file, going to Layer Transparency Add Alpha Channel.

If your image has already had background behind it (like a screenshot), you can then select it using the Fuzzy select tool (or by pressing A), selecting the background by clicking it, and then press Delete.

In order to remove the Alpha Channel, you need to go again to the "transparency" menu of the steps above, but select "Remove Alpha Channel".

Verical rectanle-shaped images tips

This one is quite a problem when uploading images. If the height of the image is larger by over 4-8% than the width, there should be a problem that will cause the image to ve slightly higher than it should, and strech the infobox (in other cases it is mostly not really important).

The problem in a nutshell:

When using an mage that is much higher than its height in an infobox, it causes the image to be very high.

Why?

Because the default size of an image in our infoboxes is 120px (the size doesn't matter but what happens when resizing); the server sets a width of 120px to the image, but to kep the propoortions, it has to resize the height as well. If the width is x and the hight is larger than x, the width will be 120px and the hight will be much larger.

So how do i solve this?

When accomplishing your image in GIMP, mark all the document (Ctrl+A) and copy (Ctrl+C). Click "Open a new file". The size it will suggest equals to the size of the file you are using. If the height is larger than the width, simply change the width to the value of the height, and open the document. Paste your image, and now you have a square image! it means the height will always be equal to the height.

Make a 3-region-gradient rectangle shapes

3-region-gradient-tutorial

An example to a 3-region gradient image: The

The result of this is shown in the image on the right.

  1. Open a new document, which its height equals its width (on this example, i selected 600px). Make sure to select "Transparency" for the background.
  2. Press Ctrl+Shift+N for creating a new layer. Use the same size as your file size. Make sure "transparent" is selected.
  3. Press Ctrl+L, to open the layer list. Select the top layer.
  4. Now, using the Rectangle select (R), create a rectangle that its height is the same as your image's height, and its width is 1px. Draw it on the very left area of the canvas.
  5. Now, use 2 colors you'd like to use for 2 of the 3 gradients.
  6. Now, using the Blend Tool (L), start a gradient from the top side of the rectangle select to its bottom side.
    • Tip: You can use Inkscape for making an accurate version for this.
  7. Now, using the Scale Tool (T), select your object. change its width to 100% of your file width (on this example, 600 pixels).
    • As you can see, the more you look to the right, the more transparent the shape is.
  8. Now, select your bottom layer. Using the Bucket Fill Tool (B), fill in the canvas. As you can see, on areas on which the original gradients are transparent, the image would become more and more yellow- depends on the distance from the left and the shade.
    • Note I chose Cyan (#00ffff) and lime green (#00ff00) for the first 2 colors, and yellow (#ffff00) for the bottom layer's color.
  9. For saving as PNG, mark the top layer, and select "Merge Down".

Another Way

Make a 2-color gradient in the entire canvas. Select another color to use as a gradient source, but instead of using the Forground to Background selection in the Blend Tool, use "Forground to Transparent".

Applications

  • You can use it for all sorts of images, such as images of color selections.
  • On the stage with the bottom layer, you can also use the Blend Tool for having another gradient source.
  • You can also choose a width of 50% of the canvas, duplicate it and flip it horizontally. Then you would be able to create a different shape for your gradients.

Automatically crop an image

You can automatically to fit the file width and height to auto by going to (in the upper menus):
Image Autocrop Image
Very useful for large images.

Viewing animations while editing

You can view animations in GIMP's interface by going to:
Filters Animation Playback

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