I = image_alpha!(img::GMTimage; alpha_ind::Integer, alpha_vec::Vector{Integer}, alpha_band::UInt8)

keywords: GMT, Julia, image transparency

Change the alpha transparency of the GMTimage object img. If the image is indexed, one can either change just the color index that will be made transparent by using alpha_ind=n or provide a vector of transaparency values in the range [0 255]; This vector can be shorter than the orginal number of colors. Use alpha_band to change, or add, the alpha of true color images (RGB).


Change to the third color in cmap to represent the new transparent color

image_alpha!(img, alpha_ind=3)

Change to the first 6 colors in cmap by assigning them random values

image_alpha!(img, alpha_vec=round.(Int32,rand(6).*255))

See Also

image_cpt!, ind2rgb