Delphi 6：如何使用具有 Alpha 通道的 TextOut 创建位图？
我将描述我的总体目标，以防我提出的问题不是获得我正在寻找的答案的最佳形式。我有一个围绕 X 轴旋转的单词球体或“单词球”。当单词旋转到后面时（Z坐标从-1到1，从前到后），我打算更改每个单词的大小和不透明度，以便“前面”中的单词100％不透明且全尺寸，并且单词后面较小且有些透明。我更愿意使用直接的 Delphi 代码来完成此操作，并避免使用 Direct3D 等。我已经有了可以正常工作的旋转代码。我只需要实现我的基于 Z 坐标的感知着色想法。
当我创建单词球时，我为每个单词动态创建一个 TImage 组件。我使用 TCanvas.TextOut() 方法以居中方式将单词“打印”到 TImage 位图。我打算使用 BitBlt 将该位图复制到保存单词球的主 Canvas 中的正确位置，因为 BitBlt 速度很快，并且可以动态调整位图大小，满足我的感知着色操作的要求之一。
但我不知道促进 Alpha 混合的最佳方法。我知道 Windows 有 AlphaBlend() 调用，而且使用起来似乎相当简单。但我需要知道如何创建一个位图，该位图是具有 Alpha 通道的每个字 TImage 组件的副本。请注意，在我的例子中，整个位图的 Alpha 通道将具有统一的值，因为我希望根据 Z 坐标将不透明度均匀地应用于整个单词。
动态创建的 TImage 组件（带有使用 TCanvas.TextOut() 制作的位图）是否有 Alpha 通道？如果没有，我如何创建一个，或者实时创建一个 TImage 位图的副本，该副本具有要传递给 AlphaBlend() 调用的 Alpha 通道？如果有更好的方法来完成这一切，请告诉我。
I'll describe my overall goal in case the question I asked isn't in the best form to get the answer I'm looking for. I have a sphere of words or "word ball" that spins around the X axis. As words spin to the back (Z coordinate goes from -1 to 1, front to back), I intend to change the size and the opacity of each word so that words in "front" are 100% opaque and full-sized and words in back are smaller and somewhat transparent. I would prefer to do this with straight Delphi code and avoid things like Direct3D, etc. I already have the rotation code working fine. I just need to implement my Z coordinate based perceptual shading idea.
When I create the word ball I dynamically create a TImage component for each word. I "print" the word to the TImage bitmap using the TCanvas.TextOut() method in a centered manner. I intend to use BitBlt to copy that bitmap to the correct location in the main Canvas that holds the word ball, because BitBlt is fast and can resize bitmaps on-the-fly, meeting one of the requirements for my perceptual shading operation.
But I don't know the best way to facilitate the Alpha blending. I know that Windows has the AlphaBlend() call and it seems fairly straightforward to use. But I would need to know how to create a bitmap that is a copy of the per-word TImage component that has an alpha channel. Note, in my case the entire bitmap will have a uniform value for the alpha channel since I want the opacity to be applied uniformly to the entire word, based on it's Z coordinate.
Does a dynamically created TImage component with a bitmap made by using TCanvas.TextOut() have an Alpha channel? If not, how do I create one, or create a copy of a TImage bitmap in real time that does have an Alpha channel to be passed to the AlphaBlend() call? If there's a better way to do all this just let me know.
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文档说：
所以我想如果您只想要整个图像恒定的透明度，您的图像不必采用任何特殊格式。
另一方面，我认为这不是你想要的。想象一下一个矩形区域的文本与另一个区域重叠：虽然矩形的某些部分可能没有文本，但它们仍然会以半透明的白色或任何您作为背景、颜色的颜色绘制。
The documentation says:
So I guess your image doesn't have to be in any special format if you just want a whole image constant transparency.
On the other hand, I don't think that's what you want. Just imagine one rectangular area with text overlapping with another: although some parts of the rectangle might not have text, they'll still be drawn in a semi-transparent white, or whatever one you have as background, color.
我发现这个链接给出了如何在 Delphi 6 中进行 Alpha 混合的可靠示例，现在我可以使用它了：
http://www.delphi-central.com/tutorials/AlphaBlend.aspx
它与使用 BitBlt() 或 StretchBlt() 参数非常接近，除了最后一个参数是 alpha -混合结构并且非常容易理解。将其与上面“他自己”的评论结合起来，您就拥有了进行 Alpha 混合所需的一切。
I found this link that gives a solid example of how to do Alpha Blending in Delphi 6 and now I have it working:
http://www.delphi-central.com/tutorials/AlphaBlend.aspx
It's very close to using BitBlt() or StretchBlt() parameter-wise, except for the last parameter which is the alpha-blend structure and is very easy to understand. Combine that with the comment by "himself" above and you have all you need to do Alpha blending.