Starting at square one with image processing
briany at qldlearning.com
Thu Jul 5 18:42:10 CDT 2007
imageData is a pixel-by-pixel property. Pixels are read in rows
across and then down.
Each pixel is 4 characters long: alpha, red, green, and blue.
So for example, a white pixel would be 0,255,255,255
A black pixel would be 0,0,0,0
A red pixel: 0,255,0,0
A 50% transparent pixel: 127, red, green, blue
And so on and so forth.
Notice the black pixel - it IS a string of zeros. You might try
changing it to a red line to illuminate the difference, but that's
why you are seeing so many zeros!
> I'm trying to understand the rudiments of image processing in Run Rev.
> I used the RR pencil (image not graphic) to draw a horizontal line
> and used the following script to see how the data was stored:
> on mouseUp
> put the imagedata of img id 1003 into tData
> repeat for each char tChar in tData
> put chartonum(tChar) after results
> end repeat
> put the number of characters in results into msg box
> put results into field 1
> end mouseUp
> All I got for my troubles was string of zeros.
> So I made a small png image in Photoshop (a short horizontal black
> line) and the same script produced the following string:
> Plus a long string of similar 10 element units.
> How does this represent a black line? Am I just observing the png
> compression code? How do I get a look at data that tells me the
> image is a black line?
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