保存NSView表示忽略透明度 [英] Save NSView representation ignores transparency

问题描述

我正在尝试将文件的图标更改为 NSView 的表示形式。我正在使用以下代码来做到这一点。

I am trying to change the icon of a file to a representation of an NSView. I am using the following code to do so.

    [mainDisplay lockFocus];
    NSBitmapImageRep *rep = [[NSBitmapImageRep alloc] initWithFocusedViewRect:[mainDisplay bounds]];
    [mainDisplay unlockFocus];
    NSImage *image = [[NSImage alloc] initWithData:[rep representationUsingType:NSTIFFFileType properties:nil]];
    [[NSWorkspace sharedWorkspace] setIcon:image forFile:[savePanel filename] options:0];

这有效。它将图标完全更改为我想要的颜色，但任何透明性都变为白色。如何保持透明度？我知道它适用于Photoshop，但是可以使用Apple的框架吗？

This works. It changes the icon exactly how I would like, except for the fact that any transparency to white. How can I keep the transparency? I know it works for Photoshop, but is is possible using Apple's frameworks?

推荐答案

您无法通过这种方式获得具有透明度的图像，因为 [NSBitmapImageRep initWithFocusedViewRect：] 从窗口服务器获取一块渲染的图像，该视图的图像已经被平整为具有其他底层视图和窗口背景的图像。

You cannot get an image with transparency this way, because [NSBitmapImageRep initWithFocusedViewRect:] gets a piece of rendered image from the window server, where the view's image already flattened to an image with other underlaying views and the window's background.

您需要的是分配一个具有适当格式的干净的 NSBitmapImageRep 并在其上呈现视图的内容：

What you need is it to allocate a new clean NSBitmapImageRep with appropriate format and render the view's content on it:

NSBitmapImageRep* rep = [[NSBitmapImageRep alloc] initWithBitmapDataPlanes:nil 
pixelsWide:[mainDisplay bounds].size.width pixelsHigh:[mainDisplay bounds].size.height
bitsPerSample:8 samplesPerPixel:4 hasAlpha:YES isPlanar:NO
colorSpaceName:NSDeviceRGBColorSpace
bytesPerRow:[mainDisplay bounds].size.width * 4 bitsPerPixel:32];

[mainDisplay cacheDisplayInRect:[mainDisplay bounds] toBitmapImageRep:rep];

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