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GdiGradientFillRect
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API Explanation
The GdiGradientFill function fills rectangle and triangle structures.
Parameter Information
Declare Function GdiGradientFillRect Lib "gdi32" Alias "GdiGradientFill" (ByVal hdc As Long, pVertex As _
TRIVERTEX, ByVal dwNumVertex As Long, pMesh As GRADIENT_RECT, ByVal dwNumMesh As _
Long, ByVal dwMode As Long) As Long
· hdc
[in] Handle to the destination device context.
· pVertex
[in] Pointer to an array of TRIVERTEX structures that each define a triangle vertex.
· dwNumVertex
[in] The number of vertices in pVertex.
· pMesh
[in] Array of GRADIENT_TRIANGLE structures in triangle mode, or an array of GRADIENT_RECT structures in rectangle mode.
· dwNumMesh
[in] The number of elements (triangles or rectangles) in pMesh.
· dwMode
[in] Specifies gradient fill mode. This parameter can be one of the following values.
GRADIENT_FILL_RECT_H
In this mode, two endpoints describe a rectangle. The rectangle is defined to have a constant color (specified by the TRIVERTEX structure) for the left and right edges. GDI interpolates the color from the top to bottom edge and fills the interior.
GRADIENT_FILL_RECT_V
In this mode, two endpoints describe a rectangle. The rectangle is defined to have a constant color (specified by the TRIVERTEX structure) for the top and bottom edges. GDI interpolates the color from the top to bottom edge and fills the interior.
GRADIENT_FILL_TRIANGLE
In this mode, an array of TRIVERTEX structures is passed to GDI along with a list of array indexes that describe separate triangles. GDI performs linear interpolation between triangle vertices and fills the interior. Drawing is done directly in 24- and 32-bpp modes. Dithering is performed in 16-, 8-, 4-, and 1-bpp mode.
If the function succeeds, the return value is TRUE.
If the function fails, the return value is FALSE.
The GdiGradientFill function fills rectangle and triangle structures.
Parameter Information
Declare Function GdiGradientFillRect Lib "gdi32" Alias "GdiGradientFill" (ByVal hdc As Long, pVertex As _
TRIVERTEX, ByVal dwNumVertex As Long, pMesh As GRADIENT_RECT, ByVal dwNumMesh As _
Long, ByVal dwMode As Long) As Long
· hdc
[in] Handle to the destination device context.
· pVertex
[in] Pointer to an array of TRIVERTEX structures that each define a triangle vertex.
· dwNumVertex
[in] The number of vertices in pVertex.
· pMesh
[in] Array of GRADIENT_TRIANGLE structures in triangle mode, or an array of GRADIENT_RECT structures in rectangle mode.
· dwNumMesh
[in] The number of elements (triangles or rectangles) in pMesh.
· dwMode
[in] Specifies gradient fill mode. This parameter can be one of the following values.
GRADIENT_FILL_RECT_H
In this mode, two endpoints describe a rectangle. The rectangle is defined to have a constant color (specified by the TRIVERTEX structure) for the left and right edges. GDI interpolates the color from the top to bottom edge and fills the interior.
GRADIENT_FILL_RECT_V
In this mode, two endpoints describe a rectangle. The rectangle is defined to have a constant color (specified by the TRIVERTEX structure) for the top and bottom edges. GDI interpolates the color from the top to bottom edge and fills the interior.
GRADIENT_FILL_TRIANGLE
In this mode, an array of TRIVERTEX structures is passed to GDI along with a list of array indexes that describe separate triangles. GDI performs linear interpolation between triangle vertices and fills the interior. Drawing is done directly in 24- and 32-bpp modes. Dithering is performed in 16-, 8-, 4-, and 1-bpp mode.
If the function succeeds, the return value is TRUE.
If the function fails, the return value is FALSE.
Code
Private Type TRIVERTEX
x As Long
y As Long
Red As Integer 'Ushort value
Green As Integer 'Ushort value
Blue As Integer 'ushort value
Alpha As Integer 'ushort
End Type
Private Type GRADIENT_RECT
UpperLeft As Long 'In reality this is a UNSIGNED Long
LowerRight As Long 'In reality this is a UNSIGNED Long
End Type
Const GRADIENT_FILL_RECT_H As Long = &H0 'In this mode, two endpoints describe a rectangle. The rectangle is
'defined to have a constant color (specified by the TRIVERTEX structure) for the left and right edges. GDI interpolates
'the color from the top to bottom edge and fills the interior.
Const GRADIENT_FILL_RECT_V As Long = &H1 'In this mode, two endpoints describe a rectangle. The rectangle
' is defined to have a constant color (specified by the TRIVERTEX structure) for the top and bottom edges. GDI interpolates
' the color from the top to bottom edge and fills the interior.
Const GRADIENT_FILL_TRIANGLE As Long = &H2 'In this mode, an array of TRIVERTEX structures is passed to GDI
'along with a list of array indexes that describe separate triangles. GDI performs linear interpolation between triangle vertices
'and fills the interior. Drawing is done directly in 24- and 32-bpp modes. Dithering is performed in 16-, 8.4-, and 1-bpp mode.
Const GRADIENT_FILL_OP_FLAG As Long = &HFF
Private Declare Function GdiGradientFillRect Lib "gdi32" Alias "GdiGradientFill" (ByVal hdc As Long, pVertex _ As TRIVERTEX, ByVal dwNumVertex As Long, pMesh As GRADIENT_RECT, ByVal dwNumMesh As _ Long, ByVal dwMode As Long) As Long
Private Function LongToUShort(Unsigned As Long) As Integer
'A small function to convert from long to unsigned short
LongToUShort = CInt(Unsigned - &H10000)
End Function
Private Sub Form_Load()
'API uses pixels
Me.ScaleMode = vbPixels
End Sub
Private Sub Form_Paint()
Dim vert(1) As TRIVERTEX
Dim gRect As GRADIENT_RECT
'from black
With vert(0)
.x = 0
.y = 0
.Red = 0&
.Green = 0& '&HFF& '0&
.Blue = 0&
.Alpha = 0&
End With
'to red
With vert(1)
.x = Me.ScaleWidth
.y = Me.ScaleHeight
.Red = LongToUShort(&HFF00&)
.Green = 0&
.Blue = 0&
.Alpha = 0&
End With
gRect.UpperLeft = 0
gRect.LowerRight = 1
GdiGradientFillRect Me.hdc, vert(0), 2, gRect, 1, GRADIENT_FILL_RECT_H
End Sub
x As Long
y As Long
Red As Integer 'Ushort value
Green As Integer 'Ushort value
Blue As Integer 'ushort value
Alpha As Integer 'ushort
End Type
Private Type GRADIENT_RECT
UpperLeft As Long 'In reality this is a UNSIGNED Long
LowerRight As Long 'In reality this is a UNSIGNED Long
End Type
Const GRADIENT_FILL_RECT_H As Long = &H0 'In this mode, two endpoints describe a rectangle. The rectangle is
'defined to have a constant color (specified by the TRIVERTEX structure) for the left and right edges. GDI interpolates
'the color from the top to bottom edge and fills the interior.
Const GRADIENT_FILL_RECT_V As Long = &H1 'In this mode, two endpoints describe a rectangle. The rectangle
' is defined to have a constant color (specified by the TRIVERTEX structure) for the top and bottom edges. GDI interpolates
' the color from the top to bottom edge and fills the interior.
Const GRADIENT_FILL_TRIANGLE As Long = &H2 'In this mode, an array of TRIVERTEX structures is passed to GDI
'along with a list of array indexes that describe separate triangles. GDI performs linear interpolation between triangle vertices
'and fills the interior. Drawing is done directly in 24- and 32-bpp modes. Dithering is performed in 16-, 8.4-, and 1-bpp mode.
Const GRADIENT_FILL_OP_FLAG As Long = &HFF
Private Declare Function GdiGradientFillRect Lib "gdi32" Alias "GdiGradientFill" (ByVal hdc As Long, pVertex _ As TRIVERTEX, ByVal dwNumVertex As Long, pMesh As GRADIENT_RECT, ByVal dwNumMesh As _ Long, ByVal dwMode As Long) As Long
Private Function LongToUShort(Unsigned As Long) As Integer
'A small function to convert from long to unsigned short
LongToUShort = CInt(Unsigned - &H10000)
End Function
Private Sub Form_Load()
'API uses pixels
Me.ScaleMode = vbPixels
End Sub
Private Sub Form_Paint()
Dim vert(1) As TRIVERTEX
Dim gRect As GRADIENT_RECT
'from black
With vert(0)
.x = 0
.y = 0
.Red = 0&
.Green = 0& '&HFF& '0&
.Blue = 0&
.Alpha = 0&
End With
'to red
With vert(1)
.x = Me.ScaleWidth
.y = Me.ScaleHeight
.Red = LongToUShort(&HFF00&)
.Green = 0&
.Blue = 0&
.Alpha = 0&
End With
gRect.UpperLeft = 0
gRect.LowerRight = 1
GdiGradientFillRect Me.hdc, vert(0), 2, gRect, 1, GRADIENT_FILL_RECT_H
End Sub