图片的平滑切换处理技术

来源：作者：出处：巧巧读书 2006-09-11 进入讨论组

　　图片的平滑切换处理技术

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　　用过Anfy Java程序的用户一定不会忘记其优秀的图像效果处理技术：DUMP、DEFORM、Fireworks、SNOW、HUEROT、LAKE、LENS、ROT、WARP、WATER等等,的确让人兴奋不已。(若读者还不曾用过Anfy,可以到其相关网页http://www.AnfyTeam.com上去下载,约2917KB,V1.4.3)。但作为爱好编程的"程序员",老用别人的东西,总觉得心得不舒服,因此笔者也用VB6.0设计了出图片平滑过渡、加下雪效果这两种方法,以飨读者,而且可以将其设计成ActiveX,在您的网页中也可以使用--有时候，看着自己亲手做的东西，不管是否完美，总觉得有种自豪的感觉--也许这就叫做"自我陶醉"。

　　为了高效处理图形,当然需要用到WIN32 API,以下为常量定义及申明(用户可以利用VB6.0中API浏览器插入),我们将其存入模块API.bas中：

Attribute VB_Name = "API模块"
Const MILLICMETERCELL = 26.45836 '每一个像素点相当于多少微米
Public Const BLACKNESS = &H42
Public Const WHITENESS = &HFF0062
Public Const DSTINVERT = &H550009
Public Const NOTSRCCOPY = &H330008
Public Const NOTSRCERASE = &H1100A6
Public Const SRCAND = &H8800C6
Public Const SRCCOPY = &HCC0020
Public Const SRCERASE = &H440328
Public Const SRCINVERT = &H660046
Public Const SRCPAINT = &HEE0086

Public Type RECT
Left As Long
Top As Long
Right As Long
Bottom As Long
End Type

Public Type LOGBRUSH
lbStyle As Long
lbColor As Long
lbHatch As Long
End Type

Public Declare Function TextOut Lib "gdi32" Alias "TextOutA" (
ByVal hdc As Long, ByVal x As Long, ByVal y As Long,
ByVal lpString As String, ByVal nCount As Long) As Long

Public Declare Function SelectObject Lib "gdi32" (
ByVal hdc As Long, ByVal hObject As Long) As Long

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 SetPixel Lib "gdi32" (ByVal hdc As Long,
ByVal x As Long, ByVal y As Long, ByVal crColor As Long) As Long

Public Declare Function GetPixel Lib "gdi32" (ByVal hdc As Long,
ByVal x As Long, ByVal y As Long) As Long

Public Declare Function CreateCompatibleDC Lib "gdi32" (ByVal hdc 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 DeleteObject Lib "gdi32" (ByVal hObject As Long) As Long

Public Declare Function PatBlt Lib "gdi32" (ByVal hdc As Long, ByVal x As Long,
ByVal y As Long, ByVal nWidth As Long, ByVal nHeight As Long,
ByVal dwRop As Long) As Long

Public Declare Function CreateBrushIndirect Lib "gdi32" (lpLogBrush As LOGBRUSH) As Long

Public Declare Function FillRect Lib "user32" (ByVal hdc As Long, lpRect As RECT,
ByVal HBrush As Long) As Long

Public Declare Function DeleteDC Lib "gdi32" (ByVal hdc As Long) As Long
Public Declare Function CreateSolidBrush Lib "gdi32" (ByVal crColor As Long) As Long
Public Declare Function CreatePalette Lib "gdi32" (lpLogPalette As LOGPALETTE) As Long

Public Declare Function SelectPalette Lib "gdi32" (ByVal hdc As Long,
ByVal hPalette As Long, ByVal bForceBackground As Long) As Long

Public Declare Function GetPaletteEntries Lib "gdi32" (
ByVal hPalette As Long, ByVal wStartIndex As Long,
ByVal wNumEntries As Long, lpPaletteEntries As PALETTEENTRY) As Long

Public Declare Function GetBitmapDimensionEx Lib "gdi32" (
ByVal hBitmap As Long, lpDimension As Size) As Long

Public Declare Function GetBkColor Lib "gdi32" (ByVal hdc As Long) As Long
以下还将定义几个常用到的函数：

'返回两者中较小的一个
Public Function Min(ByVal a As Integer, ByVal b As Integer) As Integer
Min = IIf(a > b, b, a)
End Function

'返回两者中较大的一个
Public Function Max(ByVal a As Integer, ByVal b As Integer) As Integer
Max = IIf(a > b, a, b)
End Function

以下三个函数获取色彩中的各分量值
'取色彩中n的Red的值
Public Function GetRed(ByVal n As Long) As Integer
GetRed = n Mod 256&
End Function

'取色彩n中的Green的值
Public Function GetGreen(ByVal n As Long) As Integer
GetGreen = (n \ 256&) Mod 256&
End Function

'取色彩n中的Blue的值
Public Function GetBlue(ByVal n As Long) As Integer
GetBlue = n \ 65536
End Function
　　在VB6.0中,函数Len(s)将返回中字符的个数(一个汉字也是被定义为一个字符长度),而在WIN32 API TextOut()要求字符串长度将一个汉字定义为2个字符,因此需要全新的计算长度串函数
'取字符串中有多少个字符(1个汉字定义为2个字符宽度)

Public Function Strlen(ByVal s As String) As Integer
Dim i As Integer
n = Len(s)
For i = 1 To n
If Asc(Mid$(s, i, 1)) < 0 Then n = n + 1 ‘若为汉字,字符个数加1
Next i
Strlen = n
End Function
　　以下两个函数返回用户用LoadPicture(PictureFileName)函数装入的图片的高、宽度(以像素为单位),原始的用MILLICMETER为单位。

'获取位图的宽度(以像素为单位)
Public Function GetPictureWidth(ByVal p As Picture) As Integer
GetPictureWidth = Int(p.Width / MILLICMETERCELL + 0.5)
End Function

'获取位图的高度(以像素为单位)
Public Function GetPictureHeight(ByVal p As Picture) As Integer
GetPictureHeight = Int(p.Height / MILLICMETERCELL + 0.5)
End Function
　　用过Photoshop 5.0的用户,一定不会忘记Trient工具,它可将一种色彩平滑过渡到另一种色彩。以下这个函数可以帮我们完成这个任务。

'获取渐变色彩值
'入口参数：SrcColor 原色彩
' Steps 步骤数
' CurStep 当前的步子
' DstColor 目标色彩
'返回值：当前的色彩值
Public Function GetTrienColor(ByVal scrColor As Long,
ByVal dstColor As Long, ByVal Steps As Integer,
ByVal curStep As Integer) As Long
Dim sR, sG, sB, dR, dG, dB As Integer
sR = GetRed(scrColor)
sG = GetGreen(scrColor)
sB = GetBlue(scrColor)
dR = GetRed(dstColor)
dG = GetGreen(dstColor)
dB = GetBlue(dstColor)
sR = sR + curStep * (dR - sR) / Steps
sG = sG + curStep * (dG - sG) / Steps
sB = sB + curStep * (dB - sB) / Steps
GetTrienColor = RGB(sR, sG, sB)
End Function

　　以下两个函数返回用户用LoadPicture(PictureFileName)函数装入的图片的高、宽度(以像素为单位),原始的用MILLICMETER为单位。

　　以上的常见函数,用户也应该将其添加到API.bas中。

一、实现方法

　　为了从一个图片P1平滑向另一个图片P2过渡,如下图(从右到左将一红花的图片过渡到雪景的图片)：

　　若用户仔细观察,您会发现,其实可以将过渡的画面分为三个部分：原始图片P1部分、过渡效果部分和目标图片P2部分。对于原始部分和目标部分,我们可以利用Bitblt()直接SRCCOPY过去即可,因此重要的即是得处理过渡部分。

　　在上述的API.bas文件中，我们知道GetTrientColor，可以帮我们完成从一种色彩渐进到另一种色彩。我们设过渡部分的宽度为tw, 当前显示区域的高为h,显示的横坐标为x,那么从右到左过渡,即是从目标色彩渐进到原始的色彩,换句话说：在色彩成分中,目标色由100%逐减到0%,而原始色彩则有0%逐增到100%,其处理方法如下：

　　for i=0 to tw
　　　xx=x+i '当前显示的横坐标X
　　　fo