Why would it? Pixels are a screen representation. If you see 500 pixels on 
screen and read the colour values from on-screen pixels, naturally anything 
outside your 500x500 viewport will be unavailable, and naturally anything 
covering the 500 pixel viewport will obscure reading of the
"pixels" in your 
image beneath.

Ask your question in the microsoft vb.winapi.graphics newsgroup on the 
msnews.microsoft.com server.

-- 

Randy Birch
MVP Visual Basic
http://vbnet.mvps.org/
Please respond only to the newsgroups so all can benefit.


"lsilvand"  wrote in message 
news:84a880e2.0406110037.42193d15{at}posting.google.com...
: Hi,
:
: I've got some problems analyzing big pictures in VB. I wrote a program
: that loads in a picture to a picture box in a form and then proceeds
: to scan each vertical line for the colors and how many pixels there
: are of each color. The problem is that these pictures can be around
: 20000 x 4000 pixels in size and I've noticed that VB(?) doesn't load
: in(?) the part of the picture that isn't in view in the form. The form
: and the picture box are 500x500 pixels in size. If I try to, for
: example, read the color of pixel 501x501 then all I get is gibberish.
: I've tried to get around this by scrolling the picture box in the form
: so the area examined is always visible but then I got hit with another
: problem. If the form(window) is obscured by another program I get
: gibberish again.
: So, my questions are:
: 1. Is there a property that I can set for the picture box so it will
: be forced to read in the whole picture to memory?
: 2. Why do I get gibberish when my form is behind another form(window)?
: 3. Is there maybe a easier way to do it? Is it possible to allocate
: memory and then read the picture straight into it and do some pokeing
: and peeking instead of using a picture box?
:
: Regards,
: Linus
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