有没有办法将 Metal 输出捕获为位图或其他适合打印的格式？

Question

我正在使用 MTKit 将应用程序从 OpenGL 转换为 Metal。原始应用程序允许用户打印正在查看的 OpenGL 生成的屏幕（我也使用 Core Graphics 完成了此操作）。我想在 Metal 中做同样的事情。我认为很容易找到解决方案或至少找到解决问题的方法，但我被困住了。有没有人解决过这个问题，或者有没有人知道我应该寻找什么？

我是一名经验丰富的 Mac 程序员（更喜欢 Objective-C 解决方案，但我对其他一切都做了一些工作）并且是 Metal 的高级新手。

MacOS 10.15.3，所有Mac书籍。
Swift 5.
Xcode 11.2.1.

Answer 1

我假设您想保存来自 MTKView 的图像。但是这个函数应该适用于任何纹理。也不要忘记设置：framebufferOnly = false; Property.

bool takeScreenshot = true;
/// Called whenever the view needs to render a frame
- (void)drawInMTKView:(nonnull MTKView *)view
{
    // Create a new command buffer for each render pass to the current drawable
    id<MTLCommandBuffer> commandBuffer = [_commandQueue commandBuffer];
    commandBuffer.label = @"MyCommand";

    // Obtain a renderPassDescriptor generated from the view's drawable textures
    MTLRenderPassDescriptor *renderPassDescriptor = view.currentRenderPassDescriptor;
    id<MTLTexture> currentSwapChainTexture = view.currentDrawable.texture;



    // Your render code...



    [commandBuffer addCompletedHandler:^(id<MTLCommandBuffer> cb)
     {
        if(takeScreenshot)
        {
            SaveTexture(currentSwapChainTexture);
            takeScreenshot = false;
        }

    }];

    // Finalize rendering here & push the command buffer to the GPU
    [commandBuffer commit];
    // CPU <-> GPU Synchronization
    if(takeScreenshot)[commandBuffer waitUntilCompleted];

保存纹理函数：

void SaveTexture(id<MTLTexture> texture)
{
    int width = (int) texture.width;
    int height = (int) texture.height;
    int bytePerPixel = 4;
    int bytesPerRow = width * bytePerPixel;
    int bytesCount = width * height * bytePerPixel;
    int bitsPerComponent = 8;
    int bitsPerPixel = 32;

    void *imageBytes = malloc(bytesCount);
    void *destBytes = malloc(bytesCount);

    MTLRegion mtlregion = MTLRegionMake2D(0, 0, width, height);
    [texture getBytes:imageBytes bytesPerRow:bytesPerRow fromRegion:mtlregion mipmapLevel:0];

    vImage_Buffer src;
    src.data = imageBytes;
    src.width = width;
    src.height = height;
    src.rowBytes = bytesPerRow;


    vImage_Buffer dest;
    dest.data = destBytes;
    dest.width = width;
    dest.height = height;
    dest.rowBytes = bytesPerRow;

    // BGRA -> RGBA (Swap)
    const uint8_t map[4] = {2, 1, 0, 3};
    vImagePermuteChannels_ARGB8888(&src, &dest, map, kvImageNoFlags);


    CGColorSpaceRef cgColorSpaceRef = CGColorSpaceCreateWithName(kCGColorSpaceDisplayP3); //kCGColorSpaceSRGB - For sRGB
    CGBitmapInfo bitmapInfo = kCGImageAlphaPremultipliedLast | kCGBitmapByteOrder32Big;
    CGContextRef context = CGBitmapContextCreate(destBytes, width, height, bitsPerComponent, bytesPerRow, cgColorSpaceRef, bitmapInfo);
    CGImageRef cgImage = CGBitmapContextCreateImage(context);

    // Your NSImage
    NSImage * image = [[NSImage alloc] initWithCGImage:cgImage size:NSZeroSize];

    // Save to Photos
    [[PHPhotoLibrary sharedPhotoLibrary] performChanges:^
     {
        [PHAssetCreationRequest creationRequestForAssetFromImage: image];
    }

                                      completionHandler:^(BOOL success, NSError * error)
     {
        if(success) printf("Success \n");
    }];



    free(imageBytes);
    free(destBytes);
    CGColorSpaceRelease(cgColorSpaceRef);
    CGContextRelease(context);
    CGImageRelease(cgImage);
    texture = nil;
}

有没有办法将 Metal 输出捕获为位图或其他适合打印的格式？

Is there a way to capture Metal output as a bitmap or other format suitable for printing?

printing

bitmap

metal