by Thejan J Rajapakshe (7 Submissions)
Category: Graphics
Compatability: VB 6.0
Difficulty: Unknown Difficulty
Originally Published: Wed 3rd January 2007
Date Added: Mon 8th February 2021
Rating: 
(1 Votes)
Flip Mirror & Rotate
API Declarations
' add three command buttons and two pictureboxes. Load a bitmap into picture1 in design
' mode. Set both box to the same size. Routines execute 3 times faster than routines
' found in Microsoft's Knowledge Base.
VBcoders
'Const Pi = 3.14159265359
'private Declare Function SetPixel Lib "GDI32" (ByVal hDC As Integer, ByVal X As Integer, ByVal Y As Integer, ByVal crColor As Long) As Long
'private Declare Function GetPixel Lib "GDI32" (ByVal hDC As Integer, ByVal X As Integer, ByVal Y As Integer) As Long
'private Declare Function StretchBlt% Lib "GDI32" (ByVal hDC%, ByVal X%, ByVal Y%, ByVal nWidth%, ByVal nHeight%, ByVal hSrcDC%, ByVal XSrc%, ByVal YSrc%, ByVal nSrcWidth%, ByVal nSrcHeight%, ByVal dwRop&)
'Sub Form_Load ()
picture1.ScaleMode = 3
picture2.ScaleMode = 3
'End Sub
'Sub Command1_Click ()
'flip horizontal
picture2.Cls
px% = picture1.ScaleWidth
py% = picture1.ScaleHeight
retval% = StretchBlt(picture2.hDC, px%, 0, -px%, py%, picture1.hDC, 0, 0, px%, py%, SRCCOPY)
'End Sub
'Sub Command2_Click ()
'flip vertical
picture2.Cls
px% = picture1.ScaleWidth
py% = picture1.ScaleHeight
retval% = StretchBlt(picture2.hDC, 0, py%, px%, -py%, picture1.hDC, 0, 0, px%, py%, SRCCOPY)
'End Sub
'Sub Command3_Click ()
'rotate 45 degrees
picture2.Cls
Call bmp_rotate(picture1, picture2, 3.14 / 4)
'End Sub
'Sub bmp_rotate (pic1 As PictureBox, pic2 As PictureBox, ByVal theta!)
' bmp_rotate(pic1, pic2, theta)
' Rotate the image in a picture box.
' pic1 is the picture box with the bitmap to rotate
' pic2 is the picture box to receive the rotated bitmap
' theta is the angle of rotation
Dim c1x As Integer, c1y As Integer
Dim c2x As Integer, c2y As Integer
Dim a As Single
Dim p1x As Integer, p1y As Integer
Dim p2x As Integer, p2y As Integer
Dim n As Integer, r As Integer
c1x = pic1.ScaleWidth \ 2
c1y = pic1.ScaleHeight \ 2
c2x = pic2.ScaleWidth \ 2
c2y = pic2.ScaleHeight \ 2
If c2x < c2y Then n = c2y Else n = c2x
n = n - 1
pic1hDC% = pic1.hDC
pic2hDC% = pic2.hDC
For p2x = 0 To n
For p2y = 0 To n
If p2x = 0 Then a = Pi / 2 Else a = Atn(p2y / p2x)
r = Sqr(1& * p2x * p2x + 1& * p2y * p2y)
p1x = r * Cos(a + theta!)
p1y = r * Sin(a + theta!)
c0& = GetPixel(pic1hDC%, c1x + p1x, c1y + p1y)
c1& = GetPixel(pic1hDC%, c1x - p1x, c1y - p1y)
c2& = GetPixel(pic1hDC%, c1x + p1y, c1y - p1x)
c3& = GetPixel(pic1hDC%, c1x - p1y, c1y + p1x)
If c0& <> -1 Then xret& = SetPixel(pic2hDC%, c2x + p2x, c2y + p2y, c0&)
If c1& <> -1 Then xret& = SetPixel(pic2hDC%, c2x - p2x, c2y - p2y, c1&)
If c2& <> -1 Then xret& = SetPixel(pic2hDC%, c2x + p2y, c2y - p2x, c2&)
If c3& <> -1 Then xret& = SetPixel(pic2hDC%, c2x - p2y, c2y + p2x, c3&)
Next
t% = DoEvents()
Next
'End Sub
