GetDIBits 的参数问题

2012-03-28 08:59:46 412 阅读 AI 写同款 · GEO 优化AI 选题数据监测一键分发 ›

Windows GDI HBITMAP转BMP文件：GetDIBits底层实现与颜色深度转换详解在Windows桌面应用开发中，位图（Bitmap）是图像处理的基础数据结构，尤其在嵌入式设备上位机、工业视觉和游戏UI资源打包等场景中，对图像格式的精确控制至关重要。BMP文件作为Windows平台的标准位图格式，其结构由文件头、信息头、调色板和像素数据四部分组成，理解其原理是进行图像格式转换和优化的前提。通过Windows GDI提供的GetDIBits函数，开发者可以实现从内存HBITMAP句柄到标准BMP文件的深度转换，这不仅能满足不同颜色深度（如1位黑白、8位索引色、24位真彩色）的精确输出需求，阅读详情

VB声明
Declare Function GetDIBits Lib "gdi32" Alias "GetDIBits" (ByVal aHDC As Long, ByVal hBitmap As Long, ByVal nStartScan As Long, ByVal nNumScans As Long, lpBits As Any, lpBI As BITMAPINFO, ByVal wUsage As Long) As Long
说明
将来自一幅位图的二进制位复制到一幅与设备无关的位图里
返回值
Long，非零表示成功，零表示失败。在Windows 95中，返回值是返回的扫描线数量
参数表
参数类型及说明
aHDC Long，定义了与设备有关位图hBitmap的配置信息的一个设备场景的句柄
hBitmap Long，源位图的句柄。绝对不能将这幅位图选入设备场景
nStartScan Long，欲复制到DIB中的第一条扫描线的编号
nNumScans Long，欲复制的扫描线数量
lpBits Any，指向一个缓冲区的指针。这个缓冲区将用于装载采用DIB格式的信息，但不取回数据（用ByVal传递零值）
lpBI BITMAPINFO，对lpBits DIB的格式及颜色进行说明的一个结构。在BITMAPINFOHEADER结构中，从biSize到biCompression之间的所有字段都必须初始化
wUsage Long，下述常数之一：
DIB_PAL_COLORS 在颜色表中装载一个16位所以数组，它们与当前选定的调色板有关
DIB_RGB_COLORS 在颜色表中装载RGB颜色
注解
起始扫描线与起点有关。除非将BITMAPINFOHEADER结构的biHeight字段设为负值，否则起点就位于左下角

上面是我的API文档里的说明，他第2个参数说"绝对不能将这幅位图选入设备场景",这句话怎么理解呢？？

如果我这样写
mHdc = CreateCompatibleDC(0)
mDib = CreateDIBSection(mHdc, bMapinfo, DIB_RGB_COLORS, mPtr, 0, 0)
mOldDib = SelectObject(mHdc, mDib)

GetDIBits mHdc, mDib, 0, lHeight, p(1, 1), bMapinfo, DIB_RGB_COLORS
这样可以吗？还是必须把mHdc换成GetDC(0)啥的？？？

...全文

简易的灰度处理近期在进行自绘控件的开发时，时常用到灰度图像。譬如真彩色工具条中的Disable状态的图标，譬如真彩菜单Disable状态的图标等。照常来说，可以让控件的使用者去制作相应的图标。然而，为了让控件的使用者在使用控件时尽量简单，一个比较好的办法是在程序中生成Disable状态的图标。本文提供了一个简单的封装类CGrayBitmap，使用它的静态方法DoGray可以根据一个常规图片生成它的灰阅读详情

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橘子皮... 2012-03-29

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谁给写个代码例子，什么情况下不能第2个参数不能用

橘子皮... 2012-03-28

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如果是
mHdc = CreateCompatibleDC(hdc)
hBmp = CreateCompatibleBitmap(hdc, lWidth, lHeight)
SelectObject mHdc, hBmp

GetDIBits mHdc, hBmp, 0, lHeight, p(1, 1), bMapinfo, DIB_RGB_COLORS
也可以吗？？？？位图已经选入了哦

贝隆 2012-03-28

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'Example Name:DIB

Private Const BI_RGB = 0&

Private Const DIB_RGB_COLORS = 0 '  color table in RGBs

Private Type BITMAPINFOHEADER '40 bytes

        biSize As Long

        biWidth As Long

        biHeight As Long

        biPlanes As Integer

        biBitCount As Integer

        biCompression As Long

        biSizeImage As Long

        biXPelsPerMeter As Long

        biYPelsPerMeter As Long

        biClrUsed As Long

        biClrImportant As Long

End Type

Private Type RGBQUAD

        rgbBlue As Byte

        rgbGreen As Byte

        rgbRed As Byte

        rgbReserved As Byte

End Type

Private Type BITMAPINFO

        bmiHeader As BITMAPINFOHEADER

        bmiColors As RGBQUAD

End Type

Private Declare Function CreateCompatibleDC Lib "gdi32" (ByVal hdc As Long) As Long

Private Declare Function CreateDIBSection Lib "gdi32" (ByVal hdc As Long, pBitmapInfo As BITMAPINFO, ByVal un As Long, ByVal lplpVoid As Long, ByVal handle As Long, ByVal dw As Long) As Long

Private Declare Function GetDIBits Lib "gdi32" (ByVal aHDC As Long, ByVal hBitmap As Long, ByVal nStartScan As Long, ByVal nNumScans As Long, lpBits As Any, lpBI As BITMAPINFO, ByVal wUsage As Long) As Long

Private Declare Function SetDIBitsToDevice Lib "gdi32" (ByVal hdc As Long, ByVal x As Long, ByVal y As Long, ByVal dx As Long, ByVal dy As Long, ByVal SrcX As Long, ByVal SrcY As Long, ByVal Scan As Long, ByVal NumScans As Long, Bits As Any, BitsInfo As BITMAPINFO, ByVal wUsage As Long) As Long

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

Private Declare Function DeleteDC Lib "gdi32" (ByVal hdc As Long) As Long

Private Declare Function DeleteObject Lib "gdi32" (ByVal hObject As Long) As Long

Private 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

Private Declare Function GetDC Lib "user32" (ByVal hwnd As Long) As Long

Dim iBitmap As Long, iDC As Long

Private Sub Form_Paint()

    'KPD-Team 2000

    'URL: http://www.allapi.net/

    'E-Mail: KPDTeam@Allapi.net

    '-> Compile this code for better performance

    Dim bi24BitInfo As BITMAPINFO, bBytes() As Byte, Cnt As Long

    With bi24BitInfo.bmiHeader

        .biBitCount = 24

        .biCompression = BI_RGB

        .biPlanes = 1

        .biSize = Len(bi24BitInfo.bmiHeader)

        .biWidth = 100

        .biHeight = 100

    End With

    ReDim bBytes(1 To bi24BitInfo.bmiHeader.biWidth * bi24BitInfo.bmiHeader.biHeight * 3) As Byte

    iDC = CreateCompatibleDC(0)

    iBitmap = CreateDIBSection(iDC, bi24BitInfo, DIB_RGB_COLORS, ByVal 0&, ByVal 0&, ByVal 0&)

    SelectObject iDC, iBitmap

    BitBlt iDC, 0, 0, bi24BitInfo.bmiHeader.biWidth, bi24BitInfo.bmiHeader.biHeight, GetDC(0), 0, 0, vbSrcCopy

    GetDIBits iDC, iBitmap, 0, bi24BitInfo.bmiHeader.biHeight, bBytes(1), bi24BitInfo, DIB_RGB_COLORS

    For Cnt = LBound(bBytes) To UBound(bBytes)

        If bBytes(Cnt) < 50 Then

            bBytes(Cnt) = 0

        Else

            bBytes(Cnt) = bBytes(Cnt) - 50

        End If

    Next Cnt

    SetDIBitsToDevice Me.hdc, 0, 0, bi24BitInfo.bmiHeader.biWidth, bi24BitInfo.bmiHeader.biHeight, 0, 0, 0, bi24BitInfo.bmiHeader.biHeight, bBytes(1), bi24BitInfo, DIB_RGB_COLORS

    DeleteDC iDC

    DeleteObject iBitmap

End Sub

worldy 2012-03-28

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话说，既然使用CreateDIBSection，一般就不需要使用GetDIBits ，因为CreateDIBSection已经可以直接获得访问位图的指针

worldy 2012-03-28

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mHdc = CreateCompatibleDC(0)
mDib = CreateDIBSection(mHdc, bMapinfo, DIB_RGB_COLORS, mPtr, 0, 0)
mOldDib = SelectObject(mHdc, mDib)

GetDIBits mHdc, mDib, 0, lHeight, p(1, 1), bMapinfo, DIB_RGB_COLORS

CreateDIBSection前，必须为bMapinfo设置成员值就可以，但你得到的将是没有是一个全黑的位图

如果才获得窗口位图，GetDIBits 前，必须使用Bitblt将窗口位图拷贝入mHdc

GetDIBits 的参数问题

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