smith_c
asked on
VB 6.0 Graphics
I am experiencing immense frustration at the moment...
I have created an application in visual basic (v6.0) which will open up a tiff file of an a1/a2 size drawing (using a Wang Image Edit control), and will shrink the file down to 200 x 200 a convert it to an anti-aliased bitmap(using the .Zoom property of the Wang Image control, and PlgBlt ing the resultant image into a picture box).
Here is the catch - the above procedure works fine when the form is visible and uppermost on the screen - however I wish to run the application in the background, without having the form appear on the screen. Is there any way of fooling the operating system into thinking that the form is visible, so that the following piece of code works whether the form is visible or not?
Thankyou in anticipation
Chris
The subroutine I am using follows....
Private Sub ThumbImage(strFileName As String)
'Procedure to "Thumbnail" a tiff file
'Input file is an A1/A2 scanned image, in tiff format.
'Output (hopefully) is a bitmap file of maximum 200 x 200 pixels
'
' wimgThumbnail : Wang Image edit control
' picThumbnail : PictureBox control, with autoredraw property set to true
Const MAX_WIDTH As Integer = 200
Const MAX_HEIGHT As Integer = 200
Dim fromDC As Long
Dim Pll(0 To 2) As POINTAPI
Dim blnShouldScale As Boolean
Dim lNewZoom As Long
Dim lImgWidth As Long
Dim lImgHeight As Long
Dim sngAspectRatio As Single
Dim lRetVal As Long
'Display the tiff file in the Wang Control
wimgThumbnail.Image = strFileName
wimgThumbnail.Display
wimgThumbnail.Refresh
blnShouldScale = False
lImgWidth = wimgThumbnail.ImageWidth
lImgHeight = wimgThumbnail.ImageHeight
'Scale the image, so that it can be shrunk into a 200 x 200 picturebox
lNewZoom = 100
Do While ((lImgWidth * lNewZoom / 100 * 0.02) > MAX_WIDTH) Or ((lImgHeight * lNewZoom / 100 * 0.02) > MAX_HEIGHT)
blnShouldScale = True
lNewZoom = lNewZoom - 1
Loop
If (blnShouldScale) Then
wimgThumbnail.Zoom = lNewZoom
wimgThumbnail.Refresh
wimgThumbnail.SaveAs "c:\test.tif", 1, 3, 1, 0, True
wimgThumbnail.Image = "c:\test.tif"
wimgThumbnail.Display
wimgThumbnail.Refresh
End If
lImgWidth = wimgThumbnail.ImageWidth
lImgHeight = wimgThumbnail.ImageHeight
sngAspectRatio = lImgWidth / lImgHeight
If (sngAspectRatio >= 1#) Then
wimgThumbnail.Width = MAX_WIDTH + 1
wimgThumbnail.Height = MAX_HEIGHT / sngAspectRatio + 1
Else
wimgThumbnail.Height = MAX_HEIGHT + 1
wimgThumbnail.Width = MAX_WIDTH * sngAspectRatio + 1
End If
imgThumbnail.FitTo 0, True
'The image in the Wang Image edit control is now correctly scaled
imgThumbnail.Refresh
Pll(0).x = 0
Pll(0).y = 0
Pll(1).x = wimgThumbnail.Width - 1
Pll(1).y = 0
Pll(2).x = 0
Pll(2).y = wimgThumbnail.Height - 1
fromDC = GetDC(imgThumbnail.hwnd)
'Size the picture box in correct proportions
picThumbnail.Width = wimgThumbnail.Width - 1
picThumbnail.Height = wimgThumbnail.Height - 1
DoEvents
lRetVal = PlgBlt(picThumbnail.hdc, Pll(0), fromDC, 0, 0, wimgThumbnail.Width - 1, wimgThumbnail.Height - 1, 0, 0, 0)
ReleaseDC wimgThumbnail.hwnd, fromDC
'Save the picturebox image to a .bmp file
SavePicture picThumbnail.Image, "C:\test.bmp"
End Sub
I have created an application in visual basic (v6.0) which will open up a tiff file of an a1/a2 size drawing (using a Wang Image Edit control), and will shrink the file down to 200 x 200 a convert it to an anti-aliased bitmap(using the .Zoom property of the Wang Image control, and PlgBlt ing the resultant image into a picture box).
Here is the catch - the above procedure works fine when the form is visible and uppermost on the screen - however I wish to run the application in the background, without having the form appear on the screen. Is there any way of fooling the operating system into thinking that the form is visible, so that the following piece of code works whether the form is visible or not?
Thankyou in anticipation
Chris
The subroutine I am using follows....
Private Sub ThumbImage(strFileName As String)
'Procedure to "Thumbnail" a tiff file
'Input file is an A1/A2 scanned image, in tiff format.
'Output (hopefully) is a bitmap file of maximum 200 x 200 pixels
'
' wimgThumbnail : Wang Image edit control
' picThumbnail : PictureBox control, with autoredraw property set to true
Const MAX_WIDTH As Integer = 200
Const MAX_HEIGHT As Integer = 200
Dim fromDC As Long
Dim Pll(0 To 2) As POINTAPI
Dim blnShouldScale As Boolean
Dim lNewZoom As Long
Dim lImgWidth As Long
Dim lImgHeight As Long
Dim sngAspectRatio As Single
Dim lRetVal As Long
'Display the tiff file in the Wang Control
wimgThumbnail.Image = strFileName
wimgThumbnail.Display
wimgThumbnail.Refresh
blnShouldScale = False
lImgWidth = wimgThumbnail.ImageWidth
lImgHeight = wimgThumbnail.ImageHeight
'Scale the image, so that it can be shrunk into a 200 x 200 picturebox
lNewZoom = 100
Do While ((lImgWidth * lNewZoom / 100 * 0.02) > MAX_WIDTH) Or ((lImgHeight * lNewZoom / 100 * 0.02) > MAX_HEIGHT)
blnShouldScale = True
lNewZoom = lNewZoom - 1
Loop
If (blnShouldScale) Then
wimgThumbnail.Zoom = lNewZoom
wimgThumbnail.Refresh
wimgThumbnail.SaveAs "c:\test.tif", 1, 3, 1, 0, True
wimgThumbnail.Image = "c:\test.tif"
wimgThumbnail.Display
wimgThumbnail.Refresh
End If
lImgWidth = wimgThumbnail.ImageWidth
lImgHeight = wimgThumbnail.ImageHeight
sngAspectRatio = lImgWidth / lImgHeight
If (sngAspectRatio >= 1#) Then
wimgThumbnail.Width = MAX_WIDTH + 1
wimgThumbnail.Height = MAX_HEIGHT / sngAspectRatio + 1
Else
wimgThumbnail.Height = MAX_HEIGHT + 1
wimgThumbnail.Width = MAX_WIDTH * sngAspectRatio + 1
End If
imgThumbnail.FitTo 0, True
'The image in the Wang Image edit control is now correctly scaled
imgThumbnail.Refresh
Pll(0).x = 0
Pll(0).y = 0
Pll(1).x = wimgThumbnail.Width - 1
Pll(1).y = 0
Pll(2).x = 0
Pll(2).y = wimgThumbnail.Height - 1
fromDC = GetDC(imgThumbnail.hwnd)
'Size the picture box in correct proportions
picThumbnail.Width = wimgThumbnail.Width - 1
picThumbnail.Height = wimgThumbnail.Height - 1
DoEvents
lRetVal = PlgBlt(picThumbnail.hdc, Pll(0), fromDC, 0, 0, wimgThumbnail.Width - 1, wimgThumbnail.Height - 1, 0, 0, 0)
ReleaseDC wimgThumbnail.hwnd, fromDC
'Save the picturebox image to a .bmp file
SavePicture picThumbnail.Image, "C:\test.bmp"
End Sub
Just posting so I can read later..
ASKER
Sorry Erick37 - I have tried that, and it does not appear to work...
Have you tried calling the picturebox refresh method after you have PLGBlt the picture into the picture box.
This is a difference from vb 5.0 to vb6.0 where as in vb5.0 you did not need to call the refresh method after blting to a picture box in vb6.0 you do. As this is meant to save time if you have a number of blt's to the same picture box you can call the refresh once at the end rather than like in vb5.0 where it would be called automatically after each blt.
Hope this helps
Cheers
James
This is a difference from vb 5.0 to vb6.0 where as in vb5.0 you did not need to call the refresh method after blting to a picture box in vb6.0 you do. As this is meant to save time if you have a number of blt's to the same picture box you can call the refresh once at the end rather than like in vb5.0 where it would be called automatically after each blt.
Hope this helps
Cheers
James
ASKER
James_stillman
Like I say in the preamble, the routine works fine when the form is visible, but PLGBlt copies a blank bitmap to the picturebox when the form is not visible.
Thanks
Chris
Like I say in the preamble, the routine works fine when the form is visible, but PLGBlt copies a blank bitmap to the picturebox when the form is not visible.
Thanks
Chris
I'm sorry to say that I think it's not possible. Because the Bltbit must use in a visible enviroment, if it's invisible, where the position you specified, what on the position will be copied. Like your form invisible, the position won't be a picture or any think on it, only a blank there.
---That's I thought.
prefix
---That's I thought.
prefix
Does lRetVal return a success code?
Is fromDC always <> 0?
Try using StretchBlt instead of PlgBlt.
Is fromDC always <> 0?
Try using StretchBlt instead of PlgBlt.
I dont want to sound nasty but why don't you
Move 2 * Screen.Width, 0
your form before Show-ing it?
</wqw>
Move 2 * Screen.Width, 0
your form before Show-ing it?
</wqw>
ASKER
Sorry wqw, this answer makes no apparent sense (in the context of my question)
Chris
Chris
ASKER
Adjusted points to 800
ASKER
Erick37
The result with StretchBlt is the same. The subroutine works fine when the form is visible, but the bitmap blted is blank when the form is invisible.
Chris
The result with StretchBlt is the same. The subroutine works fine when the form is visible, but the bitmap blted is blank when the form is invisible.
Chris
"Is there any way of fooling the operating system into thinking that the form is visible, so that the following piece of code works whether the form is visible or not"
I suppose this way you can "fool" OS it's visible when the user can't see it.
</wqw>
I suppose this way you can "fool" OS it's visible when the user can't see it.
</wqw>
look, there is no way to blit without first showing the DC. you must be happy you can get fromDC from hwnd of a not-shown window.
don't know of a way to "fool" it (like posting WM_PAINT etc. messages) other way than plain showing it somewhere. btw, i'm not sure if showing it outside screen is not optimized to NOT send WM_PAINT at all. (meaning that even Showing it won't work:-)
</wqw>
don't know of a way to "fool" it (like posting WM_PAINT etc. messages) other way than plain showing it somewhere. btw, i'm not sure if showing it outside screen is not optimized to NOT send WM_PAINT at all. (meaning that even Showing it won't work:-)
</wqw>
look, there is no way to blit without first showing the DC. you must be happy you can get fromDC from hwnd of a not-shown window.
don't know of a way to "fool" it (like posting WM_PAINT etc. messages) other way than plain showing it somewhere. btw, i'm not sure if showing it outside screen is not optimized to NOT send WM_PAINT at all. (meaning that even Showing it won't work:-)
</wqw>
don't know of a way to "fool" it (like posting WM_PAINT etc. messages) other way than plain showing it somewhere. btw, i'm not sure if showing it outside screen is not optimized to NOT send WM_PAINT at all. (meaning that even Showing it won't work:-)
</wqw>
look, there is no way to blit without first showing the DC. you must be happy you can get fromDC from hwnd of a not-shown window.
don't know of a way to "fool" it (like posting WM_PAINT etc. messages) other way than plain showing it somewhere. btw, i'm not sure if showing it outside screen is not optimized to NOT send WM_PAINT at all. (meaning that even Showing it won't work:-)
</wqw>
don't know of a way to "fool" it (like posting WM_PAINT etc. messages) other way than plain showing it somewhere. btw, i'm not sure if showing it outside screen is not optimized to NOT send WM_PAINT at all. (meaning that even Showing it won't work:-)
</wqw>
ASKER
wqw
The painting of the Wang Image control is optimised, but is there no way of invalidating the device context when it is not visible - ie forcing a repaint.
Chris
The painting of the Wang Image control is optimised, but is there no way of invalidating the device context when it is not visible - ie forcing a repaint.
Chris
ASKER CERTIFIED SOLUTION
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pb.Autoredraw = True
pb.Visible = False
will do the trick.
Perhaps the same is true for the Wang control.