BitBlt once to memory?

[Oafo]

I'm sure it's not possible from what I know, but here goes...

I know how to blit a mask, then blit a graphic onto it to make it transparent, but how can I do this and store it in memory, retaining the transparency? I'm trying to just blit it once with transparency, then just pull it from memory whenever I need it. Possible? If so, can you give me a little push into the right direction? Thanks.

[petrus]

You can't, because the memory must have a value everywhere.

[drewski]

You might be able to do something similar to this. I'm assuming you're using normal Bitblt to do your transparent blts. Well, this involves two separate blts if I remember correctly. I can't remember the operator names (vbscrpaint/vbsrccopy) but couldn't you do one and put that in memory and then grab it when you need to do the second blt later? That way you can do one blt a head of time and save yourself from blting twice, who knows how many times, later?

This might not work but hey, its an idea.

[golgo13sf]

this will create your image and load it into a back buffer the size of your image, just use BitBlt to blit the back buffer (hdcBuffer is the variable name) to anywhere on the form. to blit to a picture box, change the form1.hdc to picture1.hdc in the CreateCompatibleBitmap function call. here is the example to blit the picture to the top left of the form

BitBlt Form1.hdc, 0, 0, Form1.ScaleWidth, Form1.ScaleHeight, hdcBuffer, 0, 0, vbSrcCopy

Public Declare Function BitBlt Lib "gdi32" (ByVal hDestDC As Long, ByVal x As Long, ByVal y As Long, ByVal nWidth As Long, ByVal nHeight As Long, ByVal hSrcDC As Long, ByVal xSrc As Long, ByVal ySrc As Long, ByVal dwRop As Long) As Long
Public Declare Function CreateCompatibleBitmap Lib "gdi32" (ByVal hdc As Long, ByVal nWidth As Long, ByVal nHeight As Long) As Long
Public Declare Function CreateCompatibleDC Lib "gdi32" (ByVal hdc As Long) As Long
Public Declare Function SelectObject Lib "gdi32" (ByVal hdc As Long, ByVal hObject As Long) As Long
Public Declare Function DeleteObject Lib "gdi32" (ByVal hObject As Long) As Long
Public Declare Function DeleteDC Lib "gdi32" (ByVal hdc As Long) As Long
Public Declare Function LoadImage Lib "user32" Alias "LoadImageA" (ByVal hInst As Long, ByVal lpsz As String, ByVal un1 As Long, ByVal n1 As Long, ByVal n2 As Long, ByVal un2 As Long) As Long
 
Public Const LR_LOADFROMFILE = &H10
 
Public Type BITMAPFILEHEADER
        bfType As Integer
        bfSize As Long
        bfReserved1 As Integer
        bfReserved2 As Integer
        bfOffBits As Long
End Type
Public Type BITMAPINFOHEADER
        biSize As Long
        biWidth As Long
        biHeight As Long
        biPlanes As Integer
        biBitCount As Integer
        biCompression As Long
        biSizeImage As Long
        biXPelsPerMeter As Long
        biYPelsPerMeter As Long
        biClrUsed As Long
        biClrImportant As Long
End Type
Public Type BitmapStruct
        FileHeader As BITMAPFILEHEADER
        InfoHeader As BITMAPINFOHEADER
End Type
 
Dim wid&
Dim hgt&
Dim bm As BitmapStruct
Dim hImage&
Dim hdcImage&
Dim hMask&
Dim hdcMask&
Dim hBuffer&
Dim hdcBuffer&
Dim FileName$
 
 
Private Sub Form_Load()
     
     FileName = app.path & "\image.bmp"
 
     GetBitmapInfo
 
    wid = bm.InfoHeader.biWidth
    hgt = bm.InfoHeader.biHeight
    hImage = LoadImage(ByVal 0&, FileName, 0, wid, hgt, LR_LOADFROMFILE)
    hdcImage = CreateCompatibleDC(0)
    SelectObject hdcImage, hImage
 
    FileName = app.path & "\mask.bmp"
 
     GetBitmapInfo
 
    wid = bm.InfoHeader.biWidth
    hgt = bm.InfoHeader.biHeight
    hMask = LoadImage(ByVal 0&, FileName, 0, wid, hgt, LR_LOADFROMFILE)
    hdcMask = CreateCompatibleDC(0)
    SelectObject hdcMask, hMask
 
    hBuffer = CreateCompatibleBitmap(Form1.hdc, wid, hgt)  'change this to picture1.hdc to blit to picture boxes
    hdcBuffer = CreateCompatibleDC(0)
    SelectObject hdcBuffer, hBuffer  
 
    BitBlt hdcBuffer, 0, 0, Form1.Width, Form1.Height, hdcMask, 0, 0, vbSrcAnd
    BitBlt hdcBuffer, 0, 0, Form1.Width, Form1.Height, hdcImage, 0, 0, vbSrcPaint
 
End Sub
 
Private Sub GetBitmapInfo()
Dim filenum&
 
    filenum = FreeFile
    Open FileName For Random As filenum Len = Len(bm)
        Get filenum, 1, bm
    Close filenum
    
    If Len(bm) = 0 Then
        Debug.Print "Bitmap header is empty"
    End If
    
End Sub

[Oafo]

Thanks Golgo, I'll try that when I get home.

[Oafo]

Ok, I did it exactly as you said, and it works, except for one thing... it causes horrible graphic glitches in the transparent area of the buffer when copied onto the main form's DC. Is it fixable? I've tried for a while messing around with it, but I can't figure anything out. Any ideas?

[golgo13sf]

i'm at work now, i'll take a look at it, post the images if you can, otherwise i'll create my own

[Oafo]

Here's what's happening. No clue as to how to fix it, I've tried a lot of things.