SetPixel Problem

Hi,

I have used the SetPixel API to fill the screen with lines, i know i could use the MoveToEx, and LineTo api's but i need to set each pixel.

When it gets to about the 7th line the program crashes.

Here is the code i put in a module...





Private Declare Function SetPixel Lib "gdi32" (ByVal hdc As Long, ByVal X As Long, ByVal Y As Long, ByVal crColor As Long) As Long
Declare Function GetWindowDC Lib "user32" (ByVal hwnd As Long) As Long

Sub Main()


For a = 1 To 1024 Step 10
For b = 1 To 768
SetPixel GetWindowDC(0), a, b, RGB(255, 0, 200)
DoEvents
Next b
SetPixel GetWindowDC(0), a, b, RGB(255, 0, 200)
DoEvents
Next a

End Sub






It also goes extremely slow!!! :rolleyes:

SetPixel is extremely slow by nature. Do a search, there are routines that are (a bit) faster.

Could you name some please.

First can I point out that in the code you gave you used:

VB Code:

GetWindowDC(0)
'Shouldnt you use this:
Public Declare Function GetDesktopWindow Lib "user32" () As Long
Public Declare Function GetWindowDC Lib "user32" (ByVal hWnd As Long) As Long
 
GetWindowDC(GetDesktopWindow)

Anyway theres a neat way of getting a pointer that points to the place in memory the picture is stored and editing it that way, see these two threads for more about it:
http://www.vbforums.com/showthread.p...hreadid=210508
http://www.vbforums.com/showthread.p...hreadid=210500

I didnt really understand those.

i dont know about the GetWindowDC thing but it seems to work fine.

If you want alternatives to SetPixel look at this thread:
http://www.vbforums.com/showthread.p...hreadid=209455

ISDP

Your variables might be being declared oddly by VB. Try declaring them explicitly before using them.

Also, NEVER EVER EVER use GetWindowDC(0) in EVERY call to SetPixel or GetPixel. It will slow your program down so very much.

Z.