Gimp is free and open source image manipulation software . This post is about all the layer mode in gimp.Twenty-one different modes can be assigned to a layer. The modes (also called “blending modes”) allow complex color changes within a layer. Modes are also very complex, but the application of the modes is not. To change a layer mode simply select the layer and then select the Mode type from the drop down. There must be more than one layer for modes to actually have any effect. The mode’s opacity can then be effected by sliding the Opacity slider either to the right or left. Some of the different modes include:
- Normal: This is the default mode and will, when the Opacity is lessened, reveal the layer underneath.
- Dissolve: The dissolve mode will take a percentage of pixels from the upper layer and replace them with pixels from the lower layer. This percentage is determined by the opacity level chosen with the slider.
- Multiply: This mode is similar to normal, but the end results will be a darker opaque upper layer than would be found with Normal.
- Screen: This mode will result in more opacity for darker colors and lesser opacity for lighter colors. Black becomes transparent and white becomes pure white.
- Dodge: This mode will result in an opacity with some inverted colors. This is useful to bring out details in shadows
- Overlay: This is a combination of two modes (Multiply and Screen) but more subtle than the originals. If a lower layer is overlaid with a darker layer, the result will be darker (but not pure black). The lower layer is overlaid with a lighter layer, the result will be lighter (but, again, not pure white).
- Difference: This might be one of the niftiest of the modes. All colors have a mathematical value and difference calculates the difference between the values of the colors between two layers. This mode is really handy when adding a gradient level above an image and then manipulating the opacity of the Difference Mode.
For most works, the Normal Mode is going to be the best fit (especially if a level of opacity is all that is needed.) But when a different type of end result for the layer opacity is required, select a different mode, move the toggle to change the level of effect, and repeat with a different mode until the desired effect is found. Some of the modes are quite similar, but have varied effects, depending upon the type and color of the layers being used. Some layers lighten color, some darken color, some even transfer color between layers. The best way to see how a mode effects a layer is to play around with each to find out which mode is best for a particular task. But when the right mode is found, it can have a very dramatic effect on the end result. (via linuxfundation )