Layers Basics
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Overview Layers are what make most image editors so powerful. Images are stacked on top of each other in the layers palette. You see a flattened version of the layers in the canvas. If you take the text tool and write something on your image, you will notice that a new layer called a Shape Layer has been created. By using the Move Tool, you can move around this layer without affecting the layer underneath. Similarly, if you apply a filter it will only apply to the layer you currently have selected in the layers palette. Using this properly will give you the best possible results, and will also allow you to be more flexible if you want to change something later. When in doubt, make a new layer. Layer Visibility Layers are shown in the layers palette with a visibility mark, picture of the layer, and the title of the layer. Clicking the little eye next to the thumbnail layer will hide it, leaving all the other layers visible. Titles can be changed at any time by double clicking on the existing text. Pro Tip: To hide all other layers, select the layer you want to remain visible then hold down the option key while clicking the eye. To return all the layers to visibility hold down the option key while clicking the eye again. |
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Blending Modes and Opacity
Above the layers list there are layer blending options as well as the opacity control. Opacity is the transparency of a layer. If you pull the slider all the way to the left, you will not be able to see the layer. If you pull it all the way to the right, you can see the layer at its fullest. To make a quick watermark on your image, put some text on your image, make sure the new Shape Layer is selected, and decrease the opacity considerably. This will make the text barely visible, but still there. Check out Tutorials for additional help with watermarking.
Layer blending modes can be difficult to understand. They control the way the layer that you have selected interacts with the layers below it. Multiply for example will make all the whites of the image transparent, but leave the blacks alone. Screen does the opposite of multiply by leaving the whites alone, but making all the blacks transparent. The best way to figure out what they do is to play with them or read this.
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Adding and Deleting Layers Below the layers, there is a plus and minus button. The plus button will create a new Bitmap layer, while the minus button will delete the currently selected layer. Be careful not to delete layers you actually want to keep. There are two different kinds of layers that can be created. One is a Bitmap Layer and the other is a Shape Layer. Bitmap Layers can be image files, pictures that you bring in from iPhoto, or things that you draw. In their simplest form they are a grid of pixels on the screen. Shape Layers are more like a set of instructions rather than pixels. You can go back at any time in a Shape Layer and change the font, the colors, or the size easily. However, if you resize a Bitmap Layer you'll start to see pixelation, or big blocks of color. You can not easily change text that is already present in a Bitmap Layer. |
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Shape Layers cannot be drawn on or erased using the eraser tool. You cannot use filters on Shape Layers. If you do try to use a filter on a Shape Layer, it will ask you if you would like to "rasterize" the layer, which is the process of turning a Shape Layer into a Bitmap Layer. If you would like to perform a filter on a Shape Layer, simply click 'OK' to this dialog box. Once a Shape Layer has been rasterized you will not be able to edit the layer as you could previously. If your layer name originally started with "Shape Layer", Acorn will replace it with "Bitmap Layer" when you rasterize.
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Grouping Layers You can group layers together by creating a Group Layer in your layer palette. A Group Layer works just like a folder. You can create a Group by right-clicking inside your layers palette. A folder icon will appear in your layers palette. You can now drag your layers into this Group Layer. Notice there is an disclosure triangle next to the eye icon. Clicking on this triangle will show or hide all the layers within this group. You can rename the Group folder by double-clicking the name and entering your own. Grouping layers is also a good way to move multiple layers at once. Handy tip:
If you have a group layer selected and you use the Edit ▸ Copy menu item, you will get a composite of the entire Group Layer on the clipboard. |
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Locking Layers Locking layers is useful if you have an object on a layer that you do not wish to move. Locking the layer it rests upon will prevent you from making unwanted changes. To lock a layer, right click on the layer you wish to lock. Then select "Lock Layer" from the menu. This is also available under the Layer menu at the top of your screen. You will notice that a small lock icon appears in the right side of the layer. Use the same process to unlock the layer. |
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Merging Layers
Layers can be merged in a few different ways. Layer ▸ Merge Down allows you to combine layers one at a time with the currently selected layer being merged with the one below it. Layer ▸ Merge Visible merges all layers that are not hidden into one single layer. Layer ▸ Flatten Image merges all layers regardless of visibility. Merging layers can be a good way of keeping your work clean and organized, but it also decreases your ability to change things later on. Consider using Edit ▸ Copy Merged and making a new image from clipboard so that your layers can be preserved in the original file.
Important Word of Warning
JPEG, the format that most images are stored in, cannot have layers. Saving out to a JPEG will flatten all of the layers into one. If you would like to save your layers so you can come back later and do more edits, save as the file format .acorn.
If you are curious about the project file used in this example, you can download it here: http://flyingmeat.com/fs/images/acorn/LayersDemo.zip.