GIMP tools - BDA

GIMP 114
When working on layers, remember that the size of the memory taken depends on the
size of the layer, not on its content.
Layer modes
There are 21 layer modes. The Mode tells GIMP how to combine each pixel in the top
layer with the pixel in the layer below it. Every layer may be subject to different modes.
The background mode, i.e. the mode of the last (bottom) layer, does not have any effect
as it does not have any layers beneath it. You should remember that effects of layer
modes are cumulative. Let’s have a brief look at layer modes:
Mode
Description
Normal
Dissolve
Multiply
Divide
Screen
The top layer completely covers the layer below it. If you
want to see the layer below, reduce the opacity of the top
layer. It is the default layer mode.
This mode dissolves the upper layer into the layer beneath
it by drawing a random pattern of pixels in areas of partial
transparency. It is useful as a painting mode, but is rarely
used as a layer mode. It should be noted that paint tools
and layers have the same modes.
This mode multiplies the pixel values (to be more precise,
numeric values of the colour) of the upper layer with those
of the layer below it and then divides the result by 255.
The result is usually a darker image.
It is another "mathematical" mode. This mode multiplies
each pixel value in the lower layer by 256 and then divides
that by the corresponding pixel value of the upper layer
plus one (adding one to the denominator avoids dividing
by zero). The resulting image is lighter than the original.
This mode inverts the values of each of the pixels in the
lower and upper layers, then multiplies them together,
divides by 255 and inverts this value again. The resulting
image is a little bit brighter and “washed out” in