如何在iOS中通过MTKView制作屏幕快照图像?

问题描述

我引用了 MetalKitEsssentials ，并通过iOS 9.1中的MetalKit创建了模型查看器应用程序.

I refer to MetalKitEssentials, and make model viewer application by MetalKit in iOS 9.1.

我想从MTKView制作屏幕快照图像(RGBA格式).但是，我只得到黑色图像.

I want to make screen shot image(RGBA Format) from MTKView.But, I get only black image.

我该怎么办?

感谢您的阅读！

代码:

@implemtntation MetalViewController
{
    MTKView *metalView;
}

- (void)viewDidLoad
{
    [super viewDidload];
    [self setup];
}

- (void)setup
{
    metalDevice = MTLCreateSystemDefaultDevice();
    commandQueue = [metalDevice newCommandQueue];
    defaultLibrary = [metalDevice newDefaultLibrary];

    metalView = [[MTKView alloc] initWithFrame:self.view.frame];
    [self.view addSubview:metalView];

    metalView.delegate = self;
    metalView.device = metalDevice;
    metalView.sampleCount = 4;
    metalView.depthStencilPixelFormat = MTLPixelFormatDepth32Float_Stencil8;
    metalView.opaque = false;
    metalView.framebufferOnly = true;
    // and more set up for Metal ...
}

// if you make screen shot, call this method.
- (IBAction)onCapture:(id)sender
{
    CGRect screenRect = [[UIScreen mainScreen] bounds];
    UIGraphicsBeginImageContextWithOptions(screenRect.size, YES, 0.0);
    CGContextRef context = UIGraphicsGetCurrentContext();
    CGContextFillRect(context, screenRect);

    // draw image to context
    [metalView.layer renderInContext:context];

    UIImage *image = UIGraphicsGetImageFromCurrentImageContext();
    UIGraphicsEndImageContext();

    UIImageWriteToSavedPhotosAlbum(image, self,
                                   @selector(completeSavedImage:didFinishSavingWithError:contextInfo:), nil);
}

- (void)completeSavedImage:(UIImage *)_image didFinishSavingWithError:(NSError *)_error contextInfo:(void *)_contextInfo
{
    if (!_error)
    {
        NSLog(@"ok");
    }
    else
    {
        NSLog(@"error");
    }
}

@end

推荐答案

自我解决.

我发现了一个类似的主题.

我为以下几点写代码.

1:使用Objective-C

1: using Objective-C

2:不使用扩展名MTLTexture

2: no using extension MTLTexture

- (IBAction)onCapture:(id)sender
{
    id<MTLTexture> lastDrawableDisplayed = [metalView.currentDrawable texture];

    int width = (int)[lastDrawableDisplayed width];
    int height = (int)[lastDrawableDisplayed height];
    int rowBytes = width * 4;
    int selfturesize = width * height * 4;

    void *p = malloc(selfturesize);

    [lastDrawableDisplayed getBytes:p bytesPerRow:rowBytes fromRegion:MTLRegionMake2D(0, 0, width, height) mipmapLevel:0];

    CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB();
    CGBitmapInfo bitmapInfo = kCGBitmapByteOrder32Little | kCGImageAlphaFirst;

    CGDataProviderRef provider = CGDataProviderCreateWithData(nil, p, selfturesize, nil);
    CGImageRef cgImageRef = CGImageCreate(width, height, 8, 32, rowBytes, colorSpace, bitmapInfo, provider, nil, true, (CGColorRenderingIntent)kCGRenderingIntentDefault);

    UIImage *getImage = [UIImage imageWithCGImage:cgImageRef];
    CFRelease(cgImageRef);
    free(p);

    NSData *pngData = UIImagePNGRepresentation(getImage);
    UIImage *pngImage = [UIImage imageWithData:pngData];
    UIImageWriteToSavedPhotosAlbum(pngImage, self,
        @selector(completeSavedImage:didFinishSavingWithError:contextInfo:), nil);
}

但是，我在getBytes方法中遇到以下exec错误.

But, I get the following exec error in getBytes method.

failed assertion `texture must not be a framebufferOnly texture.'

此错误已在以下修复程序中修复.因此，我更改了MTKView的设置.

This error has been fixed in the following fix.So, I change setting for MTKView.

metalView.framebufferOnly = false;

谢谢.

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