objective-c - 如何在 macOS Cocoa Objective-C 中快照和保存渲染的 Metal drawable？

Question

我有一个应用程序，它使用 Metal 对屏幕进行一些渲染（必要时使用 a CAMetalLayer，而不是 a MTKView），我想为用户提供将结果快照保存到磁盘的选项。在转换为 Objective-C 时尝试在https://stackoverflow.com/a/47632198/2752221上遵循答案，我首先像这样编写了一个 commandBuffer 完成回调（注意这是手动保留/释放代码，而不是 ARC；抱歉，遗留代码）：

[commandBuffer addCompletedHandler:^(id<MTLCommandBuffer> buffer) {
    [self performSelectorOnMainThread:@selector(saveImageTakingDrawable:) withObject:[drawable retain] waitUntilDone:NO];
    optionKeyPressedAndUnhandled_ = NO;
}];

我打电话后立即这样做[commandBuffer presentDrawable:drawable]；我id <CAMetalDrawable> drawable的仍在范围内。这是我的实现saveImageTakingDrawable:：

- (void)saveImageTakingDrawable:(id <CAMetalDrawable>)drawable
{
    // We need to have an image to save
    if (!drawable) { NSBeep(); return; }

    id<MTLTexture> displayTexture = drawable.texture;

    if (!displayTexture) { NSBeep(); return; }

    CIImage *ciImage = [CIImage imageWithMTLTexture:displayTexture options:nil];

    // release the metal texture as soon as we can, to free up the system resources
    [drawable release];

    if (!ciImage) { NSBeep(); return; }

    NSCIImageRep *rep = [NSCIImageRep imageRepWithCIImage:ciImage];

    if (!rep) { NSBeep(); return; }

    NSImage *nsImage = [[[NSImage alloc] initWithSize:rep.size] autorelease];
    [nsImage addRepresentation:rep];

    NSData *tiffData = [nsImage TIFFRepresentation];

    if (!tiffData) { NSBeep(); return; }

    ... filesystem cruft culminating in ...

    if ([tiffData writeToFile:filePath options:NSDataWritingWithoutOverwriting error:nil])
    {
        // play a sound to acknowledge saving
        [[NSSound soundNamed:@"Tink"] play];
        return;
    }

    NSBeep();
    return;
}

结果是“叮当”的声音和合理尺寸 (1784x1090) 的 7.8 MB .tif 文件，但它是透明的，其中没有可用的图像数据；在 Hex Fiend 中查看文件显示整个文件都是零，除了相当简短的页眉和页脚部分。

我怀疑基本方法由于某种原因存在缺陷。当我尝试这个快照时，我得到了几个控制台日志：

2020-06-04 18:20:40.203669-0400 MetalTest[37773:1065740] [CAMetalLayerDrawable texture] should not be called after already presenting this drawable. Get a nextDrawable instead.
Input Metal texture was created with a device that does not match the current context device.
Input Metal texture was created with a device that does not match the current context device.
2020-06-04 18:20:40.247637-0400 MetalTest[37773:1065740] [plugin] AddInstanceForFactory: No factory registered for id <CFUUID 0x600000297260> F8BB1C28-BAE8-11D6-9C31-00039315CD46
2020-06-04 18:20:40.281161-0400 MetalTest[37773:1065740]  HALC_ShellDriverPlugIn::Open: Can't get a pointer to the Open routine

第一个日志似乎表明，在首先呈现纹理之后，我什至不允许将纹理从可绘制对象中取出。那么......这样做的正确方法是什么？

更新：

请注意，我并不热衷于saveImageTakingDrawable:'s 代码的后面部分。我很乐意写出 PNG 而不是 TIFF，如果有办法在不使用 、 或 的情况下到达我要去的地方CIImage，NSCIImageRep那就NSImage更好了。我只是想以某种方式将drawable的纹理图像保存为PNG或TIFF 。

标签： objective-cmacoscocoametal

Answer 1

我只是想以某种方式将可绘制的纹理图像保存为 PNG 或 TIFF。

这是您可以测试的另一种方法；需要将路径设置为要保存图像文件的任何位置。

- (void) windowCapture: (id)sender {
 NSTask *task = [[NSTask alloc]init];
 [task setLaunchPath:@"/bin/sh"]; 
 NSArray *args = [NSArray arrayWithObjects: @"-c", @"screencapture -i -c -Jwindow", nil];
 [task setArguments:args]; 
 NSPipe *pipe = [NSPipe pipe];
 [task setStandardOutput:pipe]; 
 [task launch];
 [task waitUntilExit];
 int status = [task terminationStatus]; 
 NSData *dataRead = [[pipe fileHandleForReading] readDataToEndOfFile];
 NSString *pipeOutput = [[[NSString alloc] initWithData:dataRead encoding:NSUTF8StringEncoding]autorelease];
 // Tell us if there was a problem
 if (!(status == 0)){NSLog(@"Error: %@",pipeOutput);}
 [task release];
 // Get image data from pasteboard and write to file
 NSPasteboard *pboard = [NSPasteboard generalPasteboard];
 NSData *pngData = [pboard dataForType:NSPasteboardTypePNG];
 NSError *err;
 BOOL success = [pngData writeToFile:@"/Users/xxxx/Desktop/ABCD.png" options:NSDataWritingAtomic error:&err];
 if(!success){NSLog(@"Unable to write to file: %@",err);} else {NSLog(@"File written to desktop.");}
}