Library tutorials & articles
Skinning (BitBlt Introduction)
- Introduction
- BitBlt API
- Example
- Conclusion
BitBlt API
The first API function I'm going to teach you about is BitBlt.
If you already know how to use this function then this tutorial will not be of much use to you, otherwise keep on reading.
The decleration of BitBlt is a long one, check it out:
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
Don't be scared off by the complex look of it. In practice it's quite easy to use.
Let's start by going through each parameter.
The first is hDestDC and this is just a handle to the container you want to draw onto. This can be any control with a DC (which stands for device context). You can usually get the DC of a control via the hDC property. For my example we will be painting onto the form so we will use the forms hDC property for this parameter.
Then we have to pass the X & Y coordinates (in pixels) for where on the destination we want to start the painting. This is the equivilant of the Top & Left properties of VB controls. In this tutorial we will use 0 for both these values as we want the entire form painted from top to bottom.
We then specify the width & height (nWidth and nHeight) of the painting. This is equivilant to the Width & Height properties of VB controls. If the source image is larger than either of these it will be cropped (cut off at the right or bottom sides).
To cover the entire form we will need to set these as the forms height and width.
The next parameter is the source DC (hSrcDC) which is where BitBlt gets the data to be copied over. In this tutorial we will be using the DC of the picture box that contains the image.
Then we have to give BitBlt xSrc & ySrc values, these are the values that BitBlt will start copying over from. For this basic tutorial they will be set as 0 always.
You might have noticed that there is no nSrcWidth or nSrcHeight variables. That is because BitBlt uses the nWidth value for the destination width and source width.
The last parameter is what we use to tell BitBlt how to copy the image over.
VB contains it's own constants for this parameter so we might as well use them. You could define your own constants but as VB already provides them I think it's easiest to use the ones already provided.
In this tutorial we're only going to use vbSrcCopy.
Apart from my school work I put most of my effort into running my joke site, I'd like to think that it makes someone smile each day. For about 1/2 a year I've been programming more and more in serv...
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thanks for the great material you posted but unfortunatelly for me
it all is in VB6. Can you show me a VB.NET example for this problem
thanks
there's a sample code in vb.net on this website that changes text to html. maybe you can use it?
You can use a simple random XOR shift to do the 'encrypting'... as you probably know XOR of XOR gives original, so you can use the same for encoding/decoding provided the shift key is right. If you supply the file (binary) to this function, then it'll return encoded with the given key.
If you pass the encoded file, it'll return the original file.
[courier new]
Public Function EncodeDecode(Data As String, Key As Long) As String
On Error Resume Next
Dim I As Long, X As Single
Dim CharNum As Integer, RandInteger As Integer
Dim SingleChar As String * 1
Dim ReturnData As String
X = Rnd(-Key)
For I = 1 To Len(Data)
CharNum = Asc(Mid$(Data, I, 1))
RandInteger = Int(256 * Rnd)
CharNum = CharNum Xor RandInteger
SingleChar = Chr(CharNum)
ReturnData = ReturnData & SingleChar
Next I
EncodeDecode = ReturnData
End Function
[/courier new]
But how do you make a key out of password ? Convert it to a number that vastly varies according to the password...
[courier new]
Public Function ConvertPassKey(Key as String) As Long
Dim I As Integer, Num As Long
Key = LCase(Key)
Num = 1
For I = 1 To Len(Key)
Num = Num + (I * Asc(Mid(Key, I, 1)))
Next I
ConvertPassKey = Num
End Function
[/courier new]
Be VERY, VERY WARY of the data you pass to the function. A slight shifting of even a single character will ruin the entire decoding process, and you'll get junk data!!!
I suggest you do multiple "parity" checks before actually give it up for decoding....
Also, encoding/decoding takes some time... that's why i prefer my tried and tested method "mangle da header!"
Enjoy !
how to encrypt picture files using visual basic so that only certain people who know the password can see the picture
hello friends
now i am in trouble.plz help me in convert the doc file into html format using vb
programing code.
plz help me i wait yours reply
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