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ima map | mtp | rea | sto | sav | sel | rem | gsn | val | rgb | cvi | cvd | ins | sla | slc | pgr | der2 | qua | lst | ext | mag | view | del | grid | combine | alpha value | |
Description
The ima command can read and store image files; display the image and manipulate images. A three component image has RGB values for each node. Some image options are only valid for one component grids.
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An image is generated by combing RGB from three images. R from first, G from second and B from third.
alpha value r g b [delta number
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Set transparency to images. r, g and b are integers range 1-255, representing intensity of red, green and blue of the color(s) that are to be transparent. E.g. ima alpha value 255 255 255 will set 100% white to be transparent. The delta number argument is for setting transparency to fit a range of rgb colors at a distance (D) away from the given rgb values. If number is set to 10, then
D = sqrt[102 + 102 + 102] = sqrt[300] = 17.32.
This is then compared to a difference, d, calculated in each pixel, calculated this way:
d = sqr [(r-r')2 + (g-g')2 + (b-b')2] where (r-r') etc. the pixel value (r') and the given value (r). So if d is less than 17.32, transparency will be applied.
E.g. ima alpha value 255 255 255 delta 10 will set transperancy to a point that has pix-values somewhat lower than 255 255 255, e.g. 245 255 255, but not more than that formula adds up to 17.32.
Examples
Ex.1: Image to grid
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