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+----- Thread: PNG headers (/showthread.php?tid=3125)
PNG headers - Robin - 07-09-2009
PNG's header is confusing. I want to grab the image's width + height for loading it in dx8 without having to know the size beforehand.
Help?
Re: PNG headers - Robin - 07-09-2009
Darryl hooked me up with a sexy header reader for jpg + png.
Disregard this.
Re: PNG headers - Robin - 07-09-2009
Here's the code if anyone wants it.
Code:
' PNG Header data
Private Type PNGHeader
Width As Integer
Height As Integer
End TypeCode:
Private Function GetPNGSize(ByVal filename As String) As PNGHeader
Dim Buffer() As Byte
Dim ChunkSize As Long
Dim ChunkType As String
Dim f As Long
f = FreeFile()
Open filename For Binary As #f
If Err 0 Then Exit Function
If LOF(f) = 0 Then Exit Function
' Read the first 2 bytes to identifier
ReDim Buffer(0 To 1)
Get #f, , Buffer
' Get the next 6 bytes to confirms that a PNG
ReDim Buffer(0 To 5)
Get #f, , Buffer
If Buffer(0) &H4E Or Buffer(1) &H47 Or Buffer(2) &HD Or _
Buffer(3) &HA Or Buffer(4) &H1A Or Buffer(5) &HA Then
Exit Function
End If
' Dim the array. Both the chunk size and chunk type have 4 bytes
ReDim Buffer(0 To 3)
Do While True
' Get the chunk size
Get #f, , Buffer
ChunkSize = (Buffer(0) * (2 ^ 24)) + (Buffer(1) * (2 ^ 16)) + (Buffer(2) * (2 ^ 8)) + Buffer(3)
' Get the chunk type
Get #f, , Buffer
ChunkType = Chr(Buffer(0)) & Chr(Buffer(1)) & Chr(Buffer(2)) & Chr(Buffer(3))
' Set the array to chunk size all chunk
ReDim Buffer(0 To ChunkSize - 1)
Get #f, , Buffer
Select Case ChunkType
Case "IHDR"
' Main Chunk with Height, Width
GetPNGSize.Width = (Buffer(0) * (2 ^ 24)) + (Buffer(1) * (2 ^ 16)) + (Buffer(2) * (2 ^ 8)) + Buffer(3)
GetPNGSize.Height = (Buffer(4) * (2 ^ 24)) + (Buffer(5) * (2 ^ 16)) + (Buffer(6) * (2 ^ 8)) + Buffer(7)
Case "IDAT", "IEND"
Exit Do
End Select
ReDim Buffer(0 To 3)
' Jump 4 bytes
Get #f, , Buffer
Loop
Close #f
End FunctionRe: PNG headers - GIAKEN - 07-09-2009
Wow very nice...
Re: PNG headers - xp79 - 09-09-2009
From what you said I imagened the code to be ALOT simpiler,
Wow thats quite something
hock: