Message: 7
Date: Sat, 07 Jul 2007 11:40:58 +0200
From: Wilhelm Sanke <[EMAIL PROTECTED]>
Subject: Re: Starting at square one with image processing
To: [email protected]
Message-ID: <[EMAIL PROTECTED]>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
James Hurley jhurley0305 at sbcglobal.net
<mailto:use-revolution%40lists.runrev.com?Subject=Starting%20at%
20square%20one%20with%20image%20processing&In-Reply-
To=20070706134327.98049488F6E%40mail.runrev.com>
wrote:
I've discovered that I have no idea what's going on with the
imagedata function.
I thought that the imagedata was a pixel by pixel map of the image. I
tried the following handler to look at each pixel of my image:
Allow me to add some information to the recommendations you already
got from this list.
The basic format for imagedata manipulation I use in my
applications is like shown below.
Treating the image as a square enables you also to access and
change pixels according to
their positions, i.e. you could select single pixels or rectangular
parts of the picture
and manipulate only them. Changing the imagedata for an entire
image would look like here:
"put the imageData of image "x" into iData
put the height of img "x" into theight
put the width of img "x" into twidth
put 4* twidth into ro # "ro" for "row": There are 4 chars to each
pixel in a row.
repeat with i = 0 to theight - 1
repeat with j = 0 to twidth - 1
#get the color values
put (chartonum(char (i*ro + j* 4 + 2) of idata)) into tRed
put (chartonum(char (i*ro + j* 4 + 3) of idata)) into tGreen
put (chartonum(char (i*ro + j* 4 + 4) of idata)) into tBlue
#=============================
# now do whatever you want to change the values of tRed, TGreen,
and tBlue
# and then put them back into the imagedata
#==================================
put numtochar(tRed) into char (i*ro + j* 4 + 2) of idata
put numtochar(tGreen) into char (i*ro + j* 4 + 3) of idata
put numtochar(tBlue) into char (i*ro + j* 4 + 4) of idata
end repeat
end repeat
set the imageData of image "x" to iData"
I also use the "for each" format in my scripts, but this is not
necessarily faster.
I have even found cases where "for each" is slower than the double
repeat loop.
To speed up script execution it is advisable to simplify the
computation inside
the loops - especially for larger images. Such a simplified script
is not as
readable as the basic one, but it is indeed faster.
Thus, the repeat loop from above could be changed to:
"repeat with i = 0 to theight - 1
put i*ro into ti
repeat with j = 0 to twidth - 1
put ti + j*4 into tij
#get the color values
put (chartonum(char tij+ 2) of idata)) into tRed
put (chartonum(char (tij+ 3) of idata)) into tGreen
put (chartonum(char (tij+ 4) of idata)) into tBlue
#=============================
# now do whatever you want to change the values of tRed, TGreen,
and tBlue
# and then put them back into the imagedata
#==================================
put numtochar(tRed) into char (tij+ 2) of idata
put numtochar(tGreen) into char (tij+ 3) of idata
put numtochar(tBlue) into char (tij+ 4) of idata
end repeat
end repeat"
To produce a gray-scale image based on the red values (this looks
much better
than computing the average value of tRed, tGreen, tBlue) the inner
part of
the script examples above would be
" put (chartonum(char tij+ 2) of idata)) into tRed
put numtochar(tRed) into char (tij+ 3) of idata
put numtochar(tRed) into char (tij+ 4) of idata"
In my various "imagedata" stacks there are quite a number of
accessible scripts
that you could change and experiment with - about hundred in
stack "Imagedata toolkit 2 preview".
<http://www.sanke.org/Software/ImagedataToolkitPreview3.zip>
<http://www.sanke.org/Software/SeamlessTiles.zip>
A new imagedata stack that can handle images of any size will be
released soon.
Regards,
Wilhelm Sanke
<http://www.sanke.org/MetaMedia>
Wilhelm,
Whew! This is impressive. It will take me quite a while to digest the
content of your toolkit. Thanks for sharing it.
A good part of my problem was using an image created with the Run Rev
paint tools. They give very erratic results for the imageData.
Using you suggestions and some fussing around, I built a poor man's
pencil (a graphic square with the script below), a tool that paints a
white line onto a my image. (My image is a black square called "mine".)
Suppose I wanted to use this "pencil" as an eraser instead; what
would be the imagedata I would insert in the neighborhood of the eraser?
Jim
-----------------------------------
local MyName, tData, tImgWidth, tImgHeight, tBlankPixel, tMax, x0, y0
on mouseDown
put the name of me into myName
put the imageData of img "mine" into tData
put the rect of image "mine" into tImgRect
put item 1 of tImgRect into x0
put item 2 of tImgRect into y0
put the width of img "mine" into tImgWidth
put the height of img "mine" into tImgHeight
end mouseDown
on MouseUp
put empty into myName
end MouseUp
on mouseLeave
put empty into myName
end mouseLeave
on MouseMove x,y
if myName is empty then exit mouseMove
set the loc of me to x,y
put x-x0 + 1 into u
put y-y0 +1 into v
if within(img "mine", the loc of me) then
put (v-1)*tImgWidth + u into tPixelNumber
put 1+ (tPixelNumber-1)*4 into tImageDataCharStart
put u & space & v & space & tPixelNumber& space &
tImageDataCharStart into msg box
put NumtoChar(0)& numtochar(255) & numtochar(255) & numtochar
(255) into char tImageDataCharStart to tImageDataCharStart+3 of tData
set the imageData of img "mine" to tData
end if
end MouseMove
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