: Is there a conventional format for an alpha mask? I'm a programmer, not a graphic designer. I'm writing a custom View for Android that requires the ability to apply an alpha mask to an image.

@Si6392903

An alpha mask is just a grayscale image. Yes you have the black and the white, but the interesting part is that you can have any grey to have any level of transparency.

There are some specific points on using a png file, for example small file size and it does not generate compression artifacts like a jpg file. You could also use a tif format or a psd file... But a simple png file will do.

In the case you need transparencies for a logo, yo need to use a losless file. but actually, it can be fun to use any image or photo (from a cell phone for example), that most likley will be full color and a 24 bit compressed jpg.

It would be nice if the aplication informs that the mask:

1) Is not the same size or proportion of the target image, but in general terms you can just strech it to fit it.

2) Is a color image, and it will be converted into grayscale.

3) A warning that a png file with transparencies can not be used. That transparency will be discarded and unpredictable results may occur. (If you put a mask you can just hide the background. If you remove this mask you can either just make it white, or black or reveal the original background)

4) Is a compressed jpg and some artifacts can occur.

5) If an 8 bit file is being used inform that it probably contain dithered patterns.

In general. A png or jpg file would be great.

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@Caterina889

For universal use and since the mask is all about transparency, a standard greyscale PNG32 image would be one of the best formats to work properly.

You could use PNG8 if the mask doesn't need to be "soft" in any areas.

Beyond this, one gets into application-specific formats.

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