More on Layers

R. Craig Collins > Intro to Computer Graphics > More about Layers

More about Layers © R. Craig Collins, 2008

Previously, when discussing layers, those layers were used as an intermediate step... a holding area until we resized, rotated, etc.; but once the adjustments were made, the layers were flattened or merged into one layer that could be saved as a gif, a jpeg, or a png.

Recall from our previous discussion on layers:

We could open an image, expand the canvas size, then copy and Paste the other two graphics into the image.
In the GIMP, on occasion, when resizing the canvas, you must choose Layer\Layer to Image Size in order to use the entire Canvas.

When pasting, you may wish to anchor a floating layer into the existing layer, using Layer\Anchor Layer.

Or you could use Paste Into to drop the copied item directly into the existing layer.

Starting now, you'll see that the images should each be on separate layers, allowing us to move them around until everything lined up... so instead of anchoring the layer, you could use Edit/Paste As and choose New Layer... then we can move the items on different layers independently. You just need to make sure you have selected the proper layer in the Layers, Paths, and History dock, which normally opens on the right of the desktop.

Note: You must often choose Select/None before starting an editing job, to make sure you aren't limited to the wrong part of the image you are working on.

Note: You must often choose the correct layer before starting an editing job, to make sure you aren't limited to the wrong part of the image you are working on.
Layers Dock

But, from time to time, it might be nice to keep those layers, and not flatten the image right away. Each major graphics program typically has a filetype reserved for just this purpose...Photoshop uses the psd file type, and the GIMP uses the xcf extension.

The xcf format is the only format that can save all the GIMP features and states if you wish to continue working on a project.

So it is recommended that all major projects are saved using the xcf format while in progress, and saved as an xcf again when the final versions is ready. Then the xcf can be exported as a different file type that can be placed on the web or printed, such as jpeg or png.

To save a GIMP file with layers, choose File\Save As and choose the xcf filetype.
To create a jpeg version from this, for example, now choose File\Save As and choose the jpg filetype...
you will be prompted that the file will be exported, and the layers will be merged or the jpeg version,
BUT NO CHANGES WILL BE MADE TO THE original XCF.

Now that layers don't have to be discarded, many new opportunities become available. Layers can be hidden, allowing different versions of a file to be exported to many different filetypes.

Other Layer Tips
New layers can be a solid color, or transparent.
Layers can be rearranged; so what was near the bottom and was being obscured by a higher layer, can be moved to the top.
Click the layer in the Layers and Channels box and drag it above or below a different layer.
Note: the background layer cannot be moved, and is always at the bottom.
Layers can be duplicated. Right click the layer in the Layers and Channels box, normally on the right, and choose Duplicate Layer.
Note: as the background layer cannot be moved, the solution is to duplicate the background, and rearrange the copy. You may hide the original background layer.
Layers can be renamed. Right click the layer in the Layers and Channels box, normally on the right, and choose Edit Layer Attributes...

Making shapes on Layers
Create a new transparent layer.
Choose the foreground color you wish to use (see Setting the background and foreground colors in the GIMP)
Use the round or rectangular selection tool to 'draw' your oval or square, then choose Edit/Stroke Selection