Gimp why is color to alpha disabled

It appears that the new C2A tool in 2. Possibly a fixable oversight. In the mean time, in 2. In addition there is also a new Color erase layer blend mode.

Sign up to join this community. The best answers are voted up and rise to the top. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Learn more. How to use- "color to alpha" in GIMP when it is grayed out? Asked 3 years, 3 months ago. Active 1 year, 6 months ago. Viewed 40k times. Working with Value: values are compressed and look more alike; so contrast is reduced.

Shadows are made lighter: new details can show up but contrast is less; a compromise is necessary. Highlights are made darker. Working with Color channels: if you the use the green channel for example and set the output levels between and , all pixels with some green, even a low value, will have their green channel value shifted between and Working with Alpha channel: all Alpha values will be shifted to the range you have set.

The original image is a RGB gradient from black 0;0;0 to white ;; Value channel selected. The black slider has been moved to 63 and the white slider to The Histogram shows the compression of pixels. No pixel is less than 63, and no pixel is more than In the image, Shadows are lighter and Highlights are darker: contrast is reduced.

Auto : Performs an automatic setting of the levels. Three eyedroppers , ,. These three buttons respectively represent a white, a gray and a black eye-dropper. When you click one of these buttons, the mouse pointer takes the form of the eye-dropper it represents. Then, when clicking the image, the clicked pixel determines the white point , the black point or the mid point according to the eye-dropper you chose.

Works on all channels, even if a particular channel is selected. Above is original gradient from black to white. Below is the result after clicking with the white eye-dropper: all pixels with a value higher than that of the clicked pixel turned to white.

To make your work easier, this button lets you turn to the Curves tool with the same settings. These are common features described in Section 8. Figure Although this tool is not present in the Toolbox by default please refer to Section 1. This area appears as a more or less enlarged square when you maintain the click on a pixel. The white slider has been moved to the start of well marked Highlights.

The image lightens up. The resulting histogram down shows Highlights now, but Shadows are still predominant. Setting the balance between Shadows and Highlights. The mid slider has been moved to the left. If I add an alpha channel can't find a convenient one-click option for that, so I'm making do with adding a transparent layer and merging it to the main image.

Login and other functions on this site require JavaScript. Apr 18, 12 GIMP 2. Gimp 2. Any thoughts? Current versions Production: 2.

Download latest stable GIMP: 2. Minor adjustments to be made as Gimp ver is so advanced now, but still easy t Old Parchment Paper. In version 2. Is there another way to archiv Create an amazing electricity effect on any object!

GreenElephant about 1 month ago.