MESSAGE
| DATE | 2021-03-25 |
| FROM | Liam R E Quin
|
| SUBJECT | Re: [Hangout - NYLXS] [Gimp-user] Change background colour with
|
Sending this message again with the image compressed more, so it gets
through to the list... (3rd attempt!)
On Thu, 2021-03-25 at 17:24 +0100, Zoltán Kluik wrote:
> Dear Liam,
>
> Yes, the image is in RGB colour 8 bit.
> What does it mean?
Colour means as opposed to greyscale (just grey, no colur allowed).
RGB means that any pixel can be in any colour, as opposed to indexed
which would mean a fixed list of colours
8-bit means each of red, green, blue (RGB) can take any whole number
value from 0 to 255 - this is appropriate for JPEG images for example.
With the following image I did this:
(1) open the image in gimp
(2) select the Fuzzy Select tool from the toolbox
(3) in Tool Options, make sure the threshold is good - i used 13. The
higher this number ,the more the Fuzzy Select tool will select colours
that are not quite the one you click on.
(4) i clicked on the green background 9still with fuzzy select). This
selected eveything except the coin.
(5) i used select->grow to increase the selection by 2 pixels. This
makes sure that if e.g. there's a pet hair in the picture, it gets
selected out. But this also selects the edge of the coin, which we
don't want.
(6) then, i did Select->shrinl and entered 1 pixel, to get back the
edge of the coin.
(7) Probably we don't want an ugly hard edge so i used Select->Feather
by 1.5 pixels to soften the edge of the selection.
(8) i did edit->cut (or Control-X), to remove the green. If you don't
have the default black and white colours selected in the two small
panels under the toolbox, press d to reset them to defaults and then
do cut.
(9) then i did Image->Crop to Content, to get rid of the extra white
areas.
(10) finally i exported the image.
This is much faster to do than to describe. Maybe ten seconds at most.
Just before exporting ,i actually also used Colours->Levelsand pressed
Auto Input Levels; you may not want that; it makes the dark parts of
the image black. You can get a better result by including a photo card
(you can get them on ebay or from any photography shop) in the picture
and using the white and the black as white and black points in Levels.
It's pretty much instant although then you have to crop the photo card
out of the picture.
Interesting coin.
slave liam (ankh)
>
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