Buzz Kettles <[EMAIL PROTECTED]> wrote:
> Do you know if copypixels supports [#ink : #reverse]?
Hi Buzz,
According to Werner Sharp, the formula for reverse ink is:
destination = destination XOR source.
Truth table for XOR:
| 0 1
---|-------
0 | 1 0
|
1 | 0 1
(Though I imagine that you know this already :-)
This operation is applied to each of the bits in each 8-bit color component:
rgb(127, 0, 5) = 01111111 00000000 000000101
rgb(128, 127, 5) = 10000000 10000000 000000101
XOR 00000000 01111111 111111111
You should only be getting white pixels is if both destination and source
are the same color, as in the blue component above.
So it sounds as if you are using the same image as source and destination.
To reverse an image, you should use black as the destination. Using other
colors gives different effects, as shown in the demonstration below.
Cheers,
James
-- In a Movie Script:
on reverseInk(aTextColor, aDestinationColor)
-- Create a text member with the text "Buzz" in the chosen color
tTextMember = new(#text)
tTextMember.text = "Buzz"
tTextMember.fontSize = 18
tTextMember.font = "Arial"
tTextMember.alignment = #center
tTextMember.width = 64
if ilk(aTextColor) = #color then
tTextMember.color = aTextColor
end if
-- Convert the text to an image with an alpha channel
tSource = tTextMember.image
-- Prepare a destination image with the chosen background color
tRect = tSource.rect
tImage = image(tRect.width, tRect.height, 32)
if ilk(aDestinationColor) <> #color then
aDestinationColor = rgb(0, 0, 0) -- use black as default
end if
tImage.fill(tRect, aDestinationColor)
-- Use reverse ink to copy the text image across
tImage.copyPixels(tSource, tRect, tRect, [#ink: #reverse])
-- Create a new bitmap member from the resulting image
new(#bitmap).image = tImage
end
-- In the Message window:
-- To create white letters on a black background
reverseInk()
-- Using red text to create green letters on a blue background
reverseInk(rgb(255, 0, 0), rgb(0, 0, 255))
-- rgb(255, 0, 0) = 11111111 00000000 00000000 -- red
-- rgb (0, 0, 255) = 00000000 00000000 11111111 -- blue
-- XOR 00000000 11111111 00000000 -- green
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