XnView Software

Lost transparenñó when resize or 'Convert colours' in GIF-image. It's bug?

igor wrote:Lost transparenñó when resize or 'Convert colours' in GIF-image. It's bug?

It's not normal after a resize

Did you do a pixel resize, or use a filter? Using a resizing filter changes the color palette. When resizing a GIF, you almost always want to use pixel resize.

I try decrease size 256-color GIF-image with transparency. Truecolor-image without transparency as a result!?

igor wrote:I try decrease size 256-color GIF-image with transparency. Truecolor-image without transparency as a result!?

When you convert in RGB, an alpha channel is not created...

I want only resize! Colors convert auto to truecolor

Problem solved. Resize without lost transparency work with two top items in Resample option (Nearest Heighbour and Bilinear).

Last problem. Lost transparenñó after decrease colours ('Image -> Convert To Colours' menu item) in GIF. It's solvable?

Nearest neighbor is the pixel resize I mentioned earlier (most progs call it pixel resize, I hadn't noticed the xnview uses a different name). I'm rather surprised that bilinear doesn't change the color palette. All other filters wll change your image to true color, and remove transparency. It's simply a byproduct of how they work, and is unavoidable. To prevent this problem, simply use the nearest neighbor filter.


Changing the color depth (especially decreasing the colors) changes the color palette and will often remove or alter the transparent color (you might find that some other part of the image is suddenly transparent). Increasing the color depth -shouldn't- remove transparency as long as it's still 256 colors or less. Losing transparency while decreasing color depth can't be avoided, but it can be fixed. Go Image->Edit Colormap (or hit ctrl+M) . Now the next step is easy, but you may have to repeat it several times to find the right color:
Click on a color that you think is the color of the portion of the image you want transparent (ie, lets say you're working on my woody avatar, and it has a green background, you would select the green box on the color map. If there's more than one green box, you'll have to repeat this step until you find the correct one), then check the "enable transparency" box, then click OK. If you picked the right color, the background should now be transparent. If not, simply hit ctrl+M again and select a different color, then click OK. Repeat as needed until you find the right color.

(It sounds more complicated than it really is, it's difficult to explain something adequately with just words. Just give it a try, and refer back to this post if you need to.)

Thanks all!