Contents of the Image menu
The Image menu contains commands that use or affect the entire image in some way, not just the active layer or some other specific part of the image.
This command can be accessed from an image menubar as
-> ."Crop Image" crops the image to the selection bounds, by removing any strips at the edges whose contents are all completely unselected. Areas that are partially selected (for example, by feathering) are not cropped away. If no selection exists for the image, the menu entry will be insensitive.
This command can be accessed from an image menubar as
-> ."Autocrop Image" removes borders from an image. It searches the active layer for the largest possible border area that all has the same color, and then crops this area from the image, just as though you had used the Crop tool.
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Caution |
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Note carefully that this command only uses the active layer of the image to find borders. If other layers have color variations extending into the border zone of the active layer, they will be cropped away. |
This command can be accessed from an image menubar as
-> ."Merge Visible Layers" merges all layers of the image for which an "eye" symbol is shown in the Layers dialog into a single layer, leaving non-visible layers untouched. It is useful for merging a set of layers that may be scattered around the layer list. Selecting it brings up a dialog that asks you to choose between three options for the size of the final, merged layer: "Expanded as necessary" means that it will be made as small as possible without losing any of the contents of the merged layers; "Clipped to image" means it will be set to the size of the image and any layer contents outside the image bounds will be lost; and "Clipped to bottom layer" means what it says.
This command can be accessed from an image menubar as
-> ."Flatten Image" causes all of the layers of the image to be merged into a single layer with no alpha channel, with the same appearance as the full image viewed from the top. If there are any areas with transparency all the way through to the bottom of the layer stack, they are mixed with the image's background color. This operation is performed as part of the process of exporting an image, if you save it in a format that does not support layers.
This command is found in
.It allows you to change the color mode of your image. Three modes are available:
You are normally working in RGB mode, well adapted to screen. See Glossary. You can change RGB to Grayscale or Indexed, but be careful: once the image saved you can no longer retrieve the RGB colors. Work on a copy.
Grayscale: Converts your image to a 256 gray level image. See Glossary.
This option opens the Convert Image to Indexed Colors dialog:
Convert Image to Indexed Colors
See Glossary for explanations about the Indexed Color Mode.
Generate Optimate Palette: This option generates the best possible palette with a default maximum number of 256 colors (classical GIF format). You can reduce this Maximum Number of Colors. This may create unwanted effects on smooth transitions. You can reduce them by using a dithering option.
Use Black and White (1-bit) Palette: This option generates line-art images.
Use Custom Palette: The button allows you to select a custom palette in a list. The number of colors is indicated for each palette. The Web palette, 216 colors, is the Web-safe palette. It was originally created by Netscape to provide colors that would look the same on both Macs and PCs and Internet Explorer 3 could manage it. Since version 4, MSIE handles a 212 colors palette... This problem of color similarity between all platforms is not solved yet and probably will never be. You have to keep to two principles in your Web page: light text on dark background or dark text on light background and never entrust an information to a color.
Some colors of the palette may not be used if your image is poorly colored. They will be removed from the palette if the option Remove Unused Colors from the Final Palette is checked.
As an indexed image contains 256 colors or less, some colors in the original image may be absent in the palette. This may result in some blotchy or solid colors in subtle color areas. These options allows you to correct these unwanted effects induced by the Palette Options.
The filter will attempt to approximate the missing color by spreading pixels of the nearest palette colors going clustering. These clustered pixels seen from a distance simulate a new color. See Glossary
Three filters are available. It's not possible to foresee what the result of a specific filter will be and you will have to try all to get the best result. The Positioned Color Dithering is well adapted to animations.
Here is the image of a smooth transition as an example:
After transformation to GIF 4 colors without dithering:
GIF 4 colors with Floyd-Sternberg (normal):
GIF 4 colors with Floyd-Sternberg-2:
Pixels may be less clustered (?).
In a GIF image transparency is coded on 1 bit: transparent or not transparent. To give an illusion of partial transparency use the option Enable Dithering of Transparency, but the semi-flatten plugin will give you a better result.