Windows窗体：使光标位图部分透明 [英] Windows Forms: Making a cursor bitmap partially transparent
问题描述
我想使用拖/放操作部分透明的图像。这是所有的设置和工作正常，但实际转换透明度有一个奇怪的副作用。由于某些原因，象素似乎在黑色背景被混合。
下图说明了问题：
图一）是原始位图。
图b）是已执行alpha混合后生产什么。显然，这是比预期的预期50％的α-滤波器变暗了许多。
图c）为所期望的效果，图像），用50％的透明度（加入到组合物与绘图程序）
我用产生trasparent图像的代码如下：
位图bmpNew =新位图（bmpOriginal.Width，bmpOriginal.Height）;
图形G = Graphics.FromImage（bmpNew）;
//使得位50％透明：
浮法[] [] = ptsArray {
新的浮动[] {1，0，0，0，0}，/ /红
新的浮动[] {0，1，0，0，0}，//绿
新的浮动[] {0，0，1，0，0}，//蓝
新浮[] {0，0，0，0.5F，0}，//阿尔法
新的浮动[] {0，0，0，0，1} //亮度
};
嘉洛斯clrMatrix =新嘉洛斯（ptsArray）;
ImageAttributes imgAttributes =新ImageAttributes（）;
imgAttributes.SetColorMatrix（clrMatrix，ColorMatrixFlag.Default，ColorAdjustType.Bitmap）;
g.DrawImage（bmpOriginal，新矩形（0，0，bmpOriginal.Width，bmpOriginal.Height），0，0，bmpOriginal.Width，bmpOriginal.Height，GraphicsUnit.Pixel，imgAttributes）;
Cursors.Default.Draw（G，新的Rectangle（bmpOriginal.Width / 2 - 8 bmpOriginal.Height / 2 - 8，32，32））;
g.Dispose（）;
imgAttributes.Dispose（）;
返回bmpNew;
有谁知道为什么alpha混合不工作？
更新我：
为了清楚起见，该代码没有工作，如果我alphablending在绘制表面的顶部。问题是，我想从现有图像创建完全半透明图像，并以此作为在拖/放操作动态游标。甚至跳过上述和只画色填充矩形88ffffff产生暗灰色颜色。 。有鬼是怎么回事的图标
更新二：
由于我reseached一大堆，相信这一定是与光标创作，我会在下面包含太多的代码。如果只有CreateIconIndirect调用之前我GetPixel样品位图，四个颜色值似乎是完整的。因此我有一种感觉，匪徒可能是hbmColor或ICONINFO结构的hbmMask成员
这里的ICONINFO结构：
公共结构ICONINFO {// http://msdn.microsoft.com/en-us/library/ms648052(VS.85).aspx
公共BOOL FICON; //图标或光标。真=图标，假=光标
公众诠释xHotspot;
公众诠释yhotspot光标;
公众的IntPtr hbmMask; //指定图标掩码位图。如果该结构限定了黑色和白色的图标，
//这个掩码被格式化，使得上半部是图标和掩码和下部
//一半是图标的XOR位掩码。在此条件下，该高度应该是偶数倍的两项。
//如果这个结构定义了一个色图标，这个面具只定义图标的AND位掩码。
公众的IntPtr hbmColor; //处理的图标颜色位图。如果这个结构定义了一个黑色的
//白色图标这个成员可以是可选的。 hbmMask的AND掩码施加与SRCAND标志到目的地; //随后，彩色位图是通过使用SRCINVERT标志施加（使用异或）到目的地
。
}
这是实际创建光标的代码：
公共静态光标CreateCursor（BMP位图，诠释xHotSpot，诠释yhotspot光标）{
ICONINFO ICONINFO =新ICONINFO（）;
的GetIconInfo（bmp.GetHicon（），REF ICONINFO）;
iconInfo.hbmColor =（IntPtr的）0;
iconInfo.hbmMask = bmp.GetHbitmap（）;
iconInfo.xHotspot = xHotSpot;
iconInfo.yHotspot = yhotspot光标;
iconInfo.fIcon = FALSE;
返回新光标（CreateIconIndirect（REF ICONINFO））;
}
两个外部函数定义如下：
函数[DllImport（user32.dll中，入口点=CreateIconIndirect）]
公共静态外部的IntPtr CreateIconIndirect（REF ICONINFO图标）;
函数[DllImport（user32.dll中）]
[返回：的MarshalAs（UnmanagedType.Bool）
公共静态外部布尔的GetIconInfo（IntPtr的惠康，楼盘ICONINFO pIconInfo）;
GDI +有许多相关的alpha混合时的问题与GDI（和Win32）互操作做。在这种情况下，调用bmp.GetHbitmap（）将与黑色背景融为一体你的形象。在CodeProject 的文章对这个问题更多的细节，以及用于将图像添加到一个解决方案。图像列表
您应该能够使用类似的代码来获取HBITMAP使用掩码：
函数[DllImport（KERNEL32.DLL）]
公共静态外部布尔RtlMoveMemory（IntPtr的DEST，IntPtr的来源，INT dwcount）;
函数[DllImport（GDI32.DLL）]
公共静态外部的IntPtr CreateDIBSection（IntPtr的HDC，[在，的MarshalAs（UnmanagedType.LPStruct）BITMAPINFO PBMI，UINT iUsage，出的IntPtr ppvBits，IntPtr的hSection， UINT dwOffset）;
公共静态的IntPtr GetBlendedHBitmap（位图位图）
{
BITMAPINFO BITMAPINFO =新BITMAPINFO（）;
bitmapInfo.biSize = 40;
bitmapInfo.biBitCount = 32;
bitmapInfo.biPlanes = 1;
bitmapInfo.biWidth = bitmap.Width;
bitmapInfo.biHeight = -bitmap.Height;
IntPtr的PixelData取出;
IntPtr的HBITMAP = CreateDIBSection（
IntPtr.Zero，BITMAPINFO，0，出PixelData取出，IntPtr.Zero，0）;
矩形范围=新的Rectangle（0，0，bitmap.Width，bitmap.Height）;
的BitmapData位图数据= bitmap.LockBits（
界，ImageLockMode.ReadOnly，PixelFormat.Format32bppArgb）;
RtlMoveMemory（
PixelData取出，bitmapData.Scan0，bitmap.Height * bitmapData.Stride）;
bitmap.UnlockBits（位图数据）;
返回HBITMAP;
}
I want to use partially transparent images in drag/drop operations. This is all set up and works fine, but the actual transformation to transparency has a weird side effect. For some reason, the pixels seem to be blended against a black background.
The following image describes the problem:
Figure a) is the original bitmap.
Figure b) is what is produced after alpha blending has been performed. Obviously this is a lot darker than the intended 50% alpha filter intended.
Figure c) is the desired effect, image a) with 50% transparency (added to the composition with a drawing program).
The code I use to produce the trasparent image is the following:
Bitmap bmpNew = new Bitmap(bmpOriginal.Width, bmpOriginal.Height);
Graphics g = Graphics.FromImage(bmpNew);
// Making the bitmap 50% transparent:
float[][] ptsArray ={
new float[] {1, 0, 0, 0, 0}, // Red
new float[] {0, 1, 0, 0, 0}, // Green
new float[] {0, 0, 1, 0, 0}, // Blue
new float[] {0, 0, 0, 0.5f, 0}, // Alpha
new float[] {0, 0, 0, 0, 1} // Brightness
};
ColorMatrix clrMatrix = new ColorMatrix(ptsArray);
ImageAttributes imgAttributes = new ImageAttributes();
imgAttributes.SetColorMatrix(clrMatrix, ColorMatrixFlag.Default, ColorAdjustType.Bitmap);
g.DrawImage(bmpOriginal, new Rectangle(0, 0, bmpOriginal.Width, bmpOriginal.Height), 0, 0, bmpOriginal.Width, bmpOriginal.Height, GraphicsUnit.Pixel, imgAttributes);
Cursors.Default.Draw(g, new Rectangle(bmpOriginal.Width / 2 - 8, bmpOriginal.Height / 2 - 8, 32, 32));
g.Dispose();
imgAttributes.Dispose();
return bmpNew;
Does anyone know why the alpha blending does not work?
Update I:
For clarity, the code does work if I'm alphablending on top of a drawn surface. The problem is that I want to create a completely semitransparent image from an existing image and use this as a dynamic cursor during drag/drop operations. Even skipping the above and only painting a filled rectangle of color 88ffffff yields a dark grey color. Something fishy is going on with the icon.
Update II:
Since I've reseached a whole lot and believe this has got something to do with the Cursor creation, I'm gonna include that code below too. If I GetPixel-sample the bitmap just before the CreateIconIndirect call, the four color values seem to be intact. Thus I have a feeling the culprits might be the hbmColor or the hbmMask members of the IconInfo structure.
Here's the IconInfo structure:
public struct IconInfo { // http://msdn.microsoft.com/en-us/library/ms648052(VS.85).aspx
public bool fIcon; // Icon or cursor. True = Icon, False = Cursor
public int xHotspot;
public int yHotspot;
public IntPtr hbmMask; // Specifies the icon bitmask bitmap. If this structure defines a black and white icon,
// this bitmask is formatted so that the upper half is the icon AND bitmask and the lower
// half is the icon XOR bitmask. Under this condition, the height should be an even multiple of two.
// If this structure defines a color icon, this mask only defines the AND bitmask of the icon.
public IntPtr hbmColor; // Handle to the icon color bitmap. This member can be optional if this structure defines a black
// and white icon. The AND bitmask of hbmMask is applied with the SRCAND flag to the destination;
// subsequently, the color bitmap is applied (using XOR) to the destination by using the SRCINVERT flag.
}
And here is the code that actually creates the Cursor:
public static Cursor CreateCursor(Bitmap bmp, int xHotSpot, int yHotSpot) {
IconInfo iconInfo = new IconInfo();
GetIconInfo(bmp.GetHicon(), ref iconInfo);
iconInfo.hbmColor = (IntPtr)0;
iconInfo.hbmMask = bmp.GetHbitmap();
iconInfo.xHotspot = xHotSpot;
iconInfo.yHotspot = yHotSpot;
iconInfo.fIcon = false;
return new Cursor(CreateIconIndirect(ref iconInfo));
}
The two external functions are defined as follows:
[DllImport("user32.dll", EntryPoint = "CreateIconIndirect")]
public static extern IntPtr CreateIconIndirect(ref IconInfo icon);
[DllImport("user32.dll")]
[return: MarshalAs(UnmanagedType.Bool)]
public static extern bool GetIconInfo(IntPtr hIcon, ref IconInfo pIconInfo);
GDI+ has a number of problems related to alpha blending when doing interop with GDI (and Win32). In this case, the call to bmp.GetHbitmap() will blend your image with a black background. An article on CodeProject gives more detail on the problem, and a solution that was used for adding images to an image list.
You should be able to use similar code to get the HBITMAP to use for the mask:
[DllImport("kernel32.dll")]
public static extern bool RtlMoveMemory(IntPtr dest, IntPtr source, int dwcount);
[DllImport("gdi32.dll")]
public static extern IntPtr CreateDIBSection(IntPtr hdc, [In, MarshalAs(UnmanagedType.LPStruct)]BITMAPINFO pbmi, uint iUsage, out IntPtr ppvBits, IntPtr hSection, uint dwOffset);
public static IntPtr GetBlendedHBitmap(Bitmap bitmap)
{
BITMAPINFO bitmapInfo = new BITMAPINFO();
bitmapInfo.biSize = 40;
bitmapInfo.biBitCount = 32;
bitmapInfo.biPlanes = 1;
bitmapInfo.biWidth = bitmap.Width;
bitmapInfo.biHeight = -bitmap.Height;
IntPtr pixelData;
IntPtr hBitmap = CreateDIBSection(
IntPtr.Zero, bitmapInfo, 0, out pixelData, IntPtr.Zero, 0);
Rectangle bounds = new Rectangle(0, 0, bitmap.Width, bitmap.Height);
BitmapData bitmapData = bitmap.LockBits(
bounds, ImageLockMode.ReadOnly, PixelFormat.Format32bppArgb );
RtlMoveMemory(
pixelData, bitmapData.Scan0, bitmap.Height * bitmapData.Stride);
bitmap.UnlockBits(bitmapData);
return hBitmap;
}
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