User Guide

Table Of Contents

CHAPTER 5. LAYERS 45

Expanded as necessary

The ﬁnal layer has the size of the largest layer of all of the visible layers. (Remember

that a layer in GIMP can be larger than the image)

Clipped to image

Will set the ﬁnal layer size equal to the image size. (Remember that layers in GIMP can

be larger than the image it self. If you have such a visible layer it will be clipped to the

image size).

Clipped to bottom layer

Will set the ﬁnal layer size equal to the bottom layer. If the bottom layer is smaller than

some of your visible layers, then the ﬁnal layer will be clipped and trimmed according to

both the size and position of the bottom layer.

5.13 Merge Down

Merges the contents of the active layer with the layer below. The resulting layer will have

the name of the lower layer.

5.14 Flatten Image

Flatten image repeatedly merges the layers down onto the background layer. This func-

tion is useful when saving to formats which don’t support layers such as JPEG.

5.15 Add Layer Mask

Adds a layer mask to the currently active layer. A layer mask controls the transparency

of the current layer . The mask itself is a grayscale image where black pixels are trans-

parent and white pixels are opaque. This works on a grey level also, allowing gradiented

masking.

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Adding a mask to a layer has the same effect as adding a secondAlpha

Channel for that layer. In fact, both are applied to the layer in the same

way, ﬁrst Alpha, then Mask.

The Add Mask Options dialog allows you to choose the initial ﬁll of the layer mask.

Black will make the layer totally transparent; White will make the layer totally opaque,

or you can choose to initialize the mask using the alpha channel of the layer. When you

choose the alpha channel the transparency of each pixel will be mapped to a grayscale

value in the mask. If you want to further manipulate the transparency in a layer, this

option can be useful.

To paint on the layer mask you have to activate it. You do that by clicking on the

thumbnail image of the mask. However you will not see the mask, you will just see the