Hi!

I am using Inkscape 0.92.3 running under Windows 7 Pro, 64-bit, Service Pack 1.

I searched the Web and looked at relevant posts in this forum but I still do not understand the difference between the Alpha Channel and Opacity.

Would someone explain it in plain English?

Thank you!

'Dr. T

Alpha is a property of the color. So, fill and stroke can have different alpha values.

Opacity is a property of the object. The whole object (a group, a circle, a path) has the same opacity value.

Moini wrote:Alpha is a property of the color ... Opacity is a property of the object ...

Dear Moini,

Thank you for your prompt reply!

Dr. T

Be aware that they also combine. So you might have a group with two objects, separated from one another: one with full alpha, and one with it set at 50%. If you then set the opacity of the group itself for 50% the result will be as though the alpha of your original objects had been 50% and 25%. But if the objects overlap, the results become harder to calculate in general terms.

You can think of it as alpha being applied to the individual elements in a group or layer. Then those elements are all combined *before* the opacity of the group is applied.

For individual elements with a flat colour I usually use opacity, since there's a popup for it at the bottom left of the status bar, so it's easy to get to. But for gradients it's better to set the alpha of the individual gradient stops (which is also done with the same control, when using on-canvas editing), as there's no way a single opacity value for the whole gradient can allow you to have separate transparent and opaque stops.

Xav wrote:Be aware that ...

Dear Xav,

Thank you for the additional information.

Dr. T