Setting Pixels - Answers to Suggestions

[Robert J Warren (Howsoft.com)]

First of all, I would like to thank the various members of the list who have
given me a number of interesting suggestions in relation to my "pixels
problem". All info has been gratefully received. Thanks also to those who
have given me advice in relation to the originally stated (but
oversimplified) drawing problem. I'm learning a lot!

In response to -
<How long does it take to copy an image?

<Maybe you can cut that in half by doing the "read the whole image
<bitmap" only once.

- the whole problem is that in the "eraser" routine the image needs to be
continuously and permanently updated and also displayed on the screen
according to every tiny movement of the eraser. The idea of copying the
whole image into a variable or array, extracting and processing a portion of
it and then replacing the whole image may be OK if it is done once, but not
repeatedly as required by the eraser routine. In Transcript, the original
copying of the image data to a variable is in fact quite quick, but the
processing, replacement and copying back of the image is far too slow.
According to the method outlined by Ken Ray in his article, I tried a test
replacement of a mere 400 pixels, and this took various seconds! Part of the
trouble is that Transcript does not appear to have instructions for simply
reading or replacing individual pixels, which might alleviate the problem to
some degree. However, ironically, as I have found out in VB, this is not the
best solution. For maximum speed you have to process the image's pixel data
directly. Putting even part of the pixel data into a variable or array for
processing slows the whole thing down too much, and don't forget that quite
complex mathematical calculations have to be performed on each pixel, which
if done correctly can also take up considerable time.

I have solved this problem in VB, but only by using non-standard pointer
routines to find and process the image data. VB also has instructions (e.g.
PaintPicture) for overlaying parts of the image data. VB is pretty fast with
regard to mathematical processing. Nevertheless, in spite of my success, the
general advice to VB programmers is to use DirectX (or C++) rather than
normal VB, which because of its complexity I am not too inclined to do at
the moment! From what I have seen so far, Transcript is more limited in all
of these respects. In short, it appears not to have been made for this kind
of graphical processing. However, if any improvements could be made in #2
(or #3???), e.g. the inclusion of instructions for setting individual
pixels, some equivalent of "PaintPicture", etc., I would be eternally
grateful.

Ken Ray himself has hit the nail on the head:

<This is something that as you identified is too slow to be done in regular
<Transcript. You need the help of an external to do the processing of the
<imageData for you. You might want to check out Chipp Walters' image tools
<at:

<http://www.altuit.com/webs/altuit2/RunRev/Downloads.htm

<There's image compositing and convolution matrix utilities there that use
<an external for speed.

<I hope it works for you,

Me too! Thanks Ray!

Bob Warren