Advanced Masking/Selection Capabilities

[Ksiundel]

How to select a part of an image for masking based on either color saturation or hue or a certain color (not RGB value but rather a color group), so that I can transform the selection to the Alpha channel.

For example, if I have a photo of a red car on a multi-color, complex background where there are NO other red colors exist on the picture, other than the body of the car, then such selection (that I need help with) suppose to select all shades of red on the photo, which is only the body of the car.

I guess you know what I'm trying to do, right? I need to create a PNG file where certain part of an image (like a body of that car) would be gray-scale alpha channel, so that by placing the image file on colored background - that would simply paint the car into another color.

See an example on this page: PNG Test

[olpezo]

there's some fails in the test black doesn't glow like that