Define base10 RGB alpha channel for Racket 2htdp/world -


i have image pulled tileset using in racket 2htdp/world program.

i can grab tile want, background not enumerated name, blue. want "hollow" pixels same color background without editing tileset image editor.

is there way make color in image transparent specifying rgb value?

i want "hollow" pixels same color background

then need use mask transparent can both transparent , in background color.


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