Help with blitting to picture box

[kiwisheep]

I need some help please.

I have a form with a picturebox on it, and what I need is some code to do the following:

MouseDown - Copy whatever is in the picturebox into a spot in memory.

MouseMove - Blit whatever is in the memory back to the picturebox.

MouseUp - Delete whatever was in memory.


I have tried playing around with CreatecompatibleDC and CreateCompatibleBitmap, but I just don't understand where I'm going wrong (maybe I just don't understand it at all). Any help would be muchly appreciated.

Thanks.

Please please please help.

[kiwisheep]

Can anyone help? I didn't think it would be that hard a question!! All I need is some code to create a device context in memory, and code to copy the contents of a picture box to that device context, and some code to delete the device context when I'm finished. Please please please....

[Nirces]

have a look here for infomation about releasing DC's

[kiwisheep]

Maybe if I posted some of my code someone might be able to tell me where I'm going wrong...

Private Sub picGrid_MouseUp(button As Integer, shift As Integer, x As Single, y As Single)
    SelectObject hDCTmp, HBMPrv
    DeleteObject hBMTmp
    DeleteDC hDCTmp
End Sub

Private Sub picGrid_MouseDown(button As Integer, shift As Integer, x As Single, y As Single)
    If button = 1 Then
        intStartx = x \ 20
        intStarty = y \ 20
        intEndx = intStartx
        intEndy = intStarty
        intOldEndx = intStartx
        intOldEndy = intStarty
        hDCTmp = CreateCompatibleDC(picGrid.hdc)
        hBMTmp = CreateCompatibleBitmap(picGrid.hdc, picGrid.ScaleWidth, picGrid.ScaleHeight)
        HBMPrv = SelectObject(hDCTmp, hBMTmp)
        picGrid.Circle (intStartx * 20 + 6, intStarty * 20 + 9), 10, RGB(255, 0, 0)
    End If
End Sub

Private Sub picGrid_MouseMove(button As Integer, shift As Integer, x As Single, y As Single)
    If button = 1 Then
        intEndx = x \ 20
        intEndy = y \ 20
        If intOldEndx <> intEndx Or intOldEndy <> intEndy Then
            BitBlt picGrid.hdc, 0, 0, picGrid.ScaleWidth, picGrid.ScaleHeight, hDCTmp, 0, 0, vbSrcCopy

Basically, what it should do is when I click, it puts a copy of what is in the picture box in memory, then draws on it. Whenever I move the mouse, I want it to draw back the original picture, then draw on it some more, but all I get at the moment when I blit back is just garbled, not what was there originally - can anyone see where I've gone wrong?

[Nirces]

far too many variables for my liking.

try adding:

BitBlt hDCTmp, 0, 0, picGrid.ScaleWidth, picGrid.ScaleHeight, picGrid.hdc, 0, 0, vbSrcCopy

after compatible DC line

Also try adding two picture boxes and copying the contents of memory into picturebox2 to see if the tempDC is being created Properley

[kiwisheep]

hmmm....I've tried your suggestions but it makes no difference. When I add the second picture box, it just blits the same rubbish to that as well. I can make it blit from the first picture box to the second, and then back again, but I don't want the second picture box to be visible, and if it's not visible, it just blits back the picture of the form where the invisible picture box is. Where oh where am I going wrong?

[Fishcake]

If you set the AutoRedraw property to true for the PicBox you don't won't visible, that should solve you're problem.

[Nirces]

Try Blting in the Image after CreateCompatibleBitmap, not DC, sorry.

I pretty sure the createbitmap, just defines a bitmap rather that makes a copy.

[kiwisheep]

Well, using two picture boxes was not quite what I had wanted to do, but as one of our apps guys here said, "Whatever works."

Thanks Fishcake, it really was as simple as setting the second pictureboxe's redraw property to true to blit from one to the other and back again.

And thanks for all your help Nirces - one day I'll come back and try to get the blitting to and from memory to work.

Thanks heaps peoples.

<- One happy chappy.