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Thread: GetPixel returns -1. how to fix?

  1. Feb 19th, 2002, 06:58 AM #1
    Arie
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    Question GetPixel returns -1. how to fix?

    Hi,

    In some times the GetPixel returns me a (-1) value.
    Why? And How can I fix it?

    Thank you,
    Arie.
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  2. Feb 19th, 2002, 07:37 AM #2
    /\/\isanThr0p
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    is it possible that you used it out of the image bounds? GetPixel uses pixels for coordinates not the vb twips so if you set your picturebox or whatever you use to twips and use them to get the position that might be the reason for the -1.
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  3. Feb 20th, 2002, 11:14 AM #3
    Arie
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    In my picturebox I use from (0,0) to (320,320).
    is it right? because it works on the most of the times.
    I don't know why it gives me (-1).

    Thank you,
    Arie.
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  4. Feb 20th, 2002, 11:45 AM #4
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    well I don't know, but the most probable reason for getting a -1 would be beeing out of bounds remember if you pic is 320 pixels wide the range is from 0 to 319 not 320, but it might be something else I don't know about.
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  6. Feb 21st, 2002, 02:16 PM #5
    Arie
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    Does anyone knows another reason for the GetPixel problem?

    Thank you for posting,
    Arie.
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  7. Feb 21st, 2002, 04:32 PM #6
    Sastraxi
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    Try messing around with AutoRedraw settings.
    All contents of the above post that aren't somebody elses are mine, not the property of some media corporation.
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  8. Feb 22nd, 2002, 02:55 PM #7
    Arie
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    My picture's autoredraw is set to false and if it wasn't my game won't work! anyone with other options??

    please help!

    thank you,
    Arie.
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  9. Feb 22nd, 2002, 06:21 PM #8
    twanvl
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    I think -1 is the default window color, if your Picturebox's BackColor is set to vbButtonFace you'll get that color.
    Just set the Picturebox's BackColor to something else (You can for example use the GetSysColor API to get the actual color of vbButtonFace)
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  11. Feb 23rd, 2002, 05:48 AM #9
    Arie
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    but,
    when I do the GetPixel function I do it for the picMain.hdc.
    not to Form1.hdc.
    any other ideas?

    thank you anyway,
    Arie.
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  12. Feb 23rd, 2002, 12:41 PM #10
    CornedBee
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    no, -1 always means error. And this is usually due to coordinates that don't exist (out of bounds).
    All the buzzt
    CornedBee

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  13. Feb 24th, 2002, 12:22 PM #11
    Arie
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    Ok, but my GetPixel is IN_BOUNDS!!!!
    That's why I'm asking what else could it be?
    It not happens all the time, it's pretty rare...
    Most of the times it works fine...

    But when it happens it ruins my game!
    What can it be? please help!

    Thank you so far,
    Arie.
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  14. Feb 24th, 2002, 01:20 PM #12
    Sastraxi
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    Well about the autoredraw thing maybe this is part of a bigger thing... why does your surface need to be False?

    Other than that, just loop until your answer is not -1.
    All contents of the above post that aren't somebody elses are mine, not the property of some media corporation.
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  15. Feb 25th, 2002, 09:59 AM #13
    joey o.
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    maybe it has to do with the color settings or the setting it was saved in? ie 8 or maybe 15 bit?
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  16. Feb 25th, 2002, 11:14 AM #14
    /\/\isanThr0p
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    well I guess it would help if you would post some code...
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  17. Feb 26th, 2002, 03:03 PM #15
    Janus
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    If your picturebox is not autoredraw, if a window is covering it, the GetPixel call will most likely fail because the pixel at that location has been erased by the window now covering it.

    Set your picturebox's autoredraw to true, and then once you draw to it, call .Refresh and VB will copy the changes to the screen for you. This prevents both flicker, and other windows from erasing your image.
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  18. Mar 1st, 2002, 11:40 AM #16
    Jotaf98
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    I know what the problem is

    If your picture is 320x320 pixels in size, you need to loop from 0 to 319 (320 - 1 ) for both the X and Y, because the coordinates are 0-based so the 0 counts too. Basically you're looping trough 321 pixels instead of 320
    Last edited by Jotaf98; Mar 1st, 2002 at 11:43 AM.
    Code:
    Temp = Me.GetIQ()
'Error 9: Overflow
'DON'T PANIC! :eek:

    To learn how to use realistic effects in your games like fire, rain, snow and magic effects, read my article on particles systems here.


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  19. Mar 1st, 2002, 11:42 AM #17
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    already said that
    seems not to help either

    maybe you should just buy a new pc
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  20. Mar 1st, 2002, 11:45 AM #18
    Jotaf98
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    It's not the 0-base... it's not the scale mode... huh... well... now that's weird

    Post the code please so we can have a look
    Code:
    Temp = Me.GetIQ()
'Error 9: Overflow
'DON'T PANIC! :eek:

    To learn how to use realistic effects in your games like fire, rain, snow and magic effects, read my article on particles systems here.


    Jotaf's Theories!
    "Cats land on their feet. Toast lands peanut butter side down. A cat with toast strapped to its back will hover above the ground in a state of quantum indecision."
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  21. Mar 1st, 2002, 07:57 PM #19
    /\/\isanThr0p
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    true true
    well why don't you paste any code. I am sure you will get help then!
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  22. Mar 3rd, 2002, 12:13 PM #20
    Jotaf98
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    Maybe he doesn't want us to steal it
    Code:
    Temp = Me.GetIQ()
'Error 9: Overflow
'DON'T PANIC! :eek:

    To learn how to use realistic effects in your games like fire, rain, snow and magic effects, read my article on particles systems here.


    Jotaf's Theories!
    "Cats land on their feet. Toast lands peanut butter side down. A cat with toast strapped to its back will hover above the ground in a state of quantum indecision."
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  23. Mar 3rd, 2002, 01:17 PM #21
    /\/\isanThr0p
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    Yeah I collect all kinds of buggy code...
    well yeah maybe we could kill the bugs, if he'd post it...

    that would make it worth stealing though....
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  24. Mar 3rd, 2002, 05:34 PM #22
    Jotaf98
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    Yeah, but if the code doesn't work it's worthless

    Look Arie, we won't be able to help unless you post the code...
    Code:
    Temp = Me.GetIQ()
'Error 9: Overflow
'DON'T PANIC! :eek:

    To learn how to use realistic effects in your games like fire, rain, snow and magic effects, read my article on particles systems here.


    Jotaf's Theories!
    "Cats land on their feet. Toast lands peanut butter side down. A cat with toast strapped to its back will hover above the ground in a state of quantum indecision."
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  25. Mar 3rd, 2002, 06:25 PM #23
    Sastraxi
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    He posted his code in a different thread.

    The 3rd reply is the code:
    http://www.vbforums.com/showthread.p...hreadid=148181
    All contents of the above post that aren't somebody elses are mine, not the property of some media corporation.
    (Just a heads-up)
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  26. Mar 5th, 2002, 01:16 PM #24
    jamieoboth
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    THAT SNEAK! He obviously didn't trust us...


    We aren't good enough for his needs... *Sniff*


    Excuse me....


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  27. Mar 5th, 2002, 02:04 PM #25
    Arie
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    Talking Thanx!!!

    It's OK!!!
    I have answered me oh right!!!
    Thank you very much!!!

    Arie.
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