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5. Working with PhotoLine / 5.7 Creating Images For The Web

### 5.7.2 Reduce Colors

In order to save images as GIF the maximum number of colors used in that image may not exceed 256. Sometimes it is efficient to reduce the number of colors in PNG and BMP, too.

In order to achieve this goal, PhotoLine offers a comfortable function accessible with Tool/Color/Reduce Colors.

This dialog is divided in two parts. The first part contains controls, that are always accessible, the second contains a tab control, that shows the subdialogs for color reduction.

The first part is used for the basic management. You can turn on the Preview, so that every change of the settings is shown immediately in the document window. This task may last quite long on complex images, therefore you can manually start a preview by pressing the Proof button.

If Preview is selected, it is possible to display the resulting GIF and PNG file size for the given settings.

Images are reduced quite often with the same settings. Because of this there are Presets and Edit. They allow you to save the current settings and call them off later. To do this you have to set the desired options in the tab control. Pressing Edit opens the management dialog where you can save the settings by entering a new name and pressing New. This new name is automatically added to the Presets list.

The second part of the Reduce Colors dialog contains the real settings for color reduction. The are separated in three subdialogs.

The General part controls the basic way of action.

You can set the desired number of colors with Color Count. The fewer colors are used in an image the smaller will usually be the resulting file. But at the same time the image quality will be lower, too. If used in the internet you should always try to keep you image files small in order to decrease the time needed for download.

Another option to influence the resulting file size and the image quality very strongly is Reduction Method. PhotoLine offers here a large variety. If you want to save a GIF file, usually Nearest Color, Error Diffusion and Horizontal Line will be best. Which one gives the best combination of quality and size, depends usually on the image and on personal preferences. and should be decided singly.

All Layers controls, whether all layers are reduced with the same color palette. Especially animated GIF files are getting smaller with this option.

At first sight it might be a bit unusual that there is a choice between Reduce Colors and Don’t Reduce Colors. This option is needed, because this function is not able to reduce the number of colors but to reduce or replace transparency, too. If you only want to remove the transparency, you should choose Don’t Reduce Colors.

The subdialog Palette is used to adjust the color palette. These are the colors used for creating the new image. There are two ways to automatically create a color palette: Optimized Octree and Optimized MedianCut. Which one is better depends on the image, but usually Optimized MedianCut is a good choice. The third mode is Standard. It uses a standard palette which is used by most web browsers, too. The last mode is Loaded, which uses the currently displayed palette. By double clicking a color this color can be modified. You can load a new palette, too.

The palette can only be changed, if Color Count is set to 256 or lower. If more than 256 colors are allowed, no palette will be used.

The Transparency subdialog controls, how to modify the transparency of an image. Many file formats - like BMP - are not able to save transparency at all. Others - like GIF - can only save 1-bit-Transparency, that means, a pixel can be visible or transparent, steps in between are not possible. And at last there are formats like PNG, that are able to save full transparency, but sadly most web browser can’t display full transparency. Therefore transparency even has to be reduced in this case.

You have the choice between three option: Don’t Dither Transparency doesn’t modify transparency, Replace Transparency by Color removes the transparency completely and replaces it by a given color and Dither Transparency allows you to create 1-bit transparency using different dithering methods.