Question

是否可以获取SCNView的屏幕截图？我正在尝试使用下面的代码，但它总是出现白色......

NSRect bounds = [window.contentView bounds];
NSImage *screenshot = [[NSImage alloc] initWithData:[window.contentView dataWithPDFInsideRect:bounds]];

当视图是标准NSView时，它可以正常工作......

Answer 1

SceneKit使用OpenGL上下文绘制。您不能像基于Quartz的上下文那样轻松地将其转换为PDF数据（由“普通”AppKit视图使用）。
但是你可以从OpenGL中获取栅格化的位图数据：

- (IBAction)takeShot:(id)sender
{
    NSString* path = @"/Users/weichsel/Desktop/test.tiff";
    NSImage* image = [self imageFromSceneKitView:self.scene];
    BOOL didWrite = [[image TIFFRepresentation] writeToFile:path atomically:YES];
    NSLog(@"Did write:%d", didWrite);
}

- (NSImage*)imageFromSceneKitView:(SCNView*)sceneKitView
{
    NSInteger width = sceneKitView.bounds.size.width * self.scene.window.backingScaleFactor;
    NSInteger height = sceneKitView.bounds.size.height * self.scene.window.backingScaleFactor;
    NSBitmapImageRep* imageRep=[[NSBitmapImageRep alloc] initWithBitmapDataPlanes:NULL
                                                                       pixelsWide:width
                                                                       pixelsHigh:height
                                                                    bitsPerSample:8
                                                                  samplesPerPixel:4
                                                                         hasAlpha:YES
                                                                         isPlanar:NO
                                                                   colorSpaceName:NSCalibratedRGBColorSpace
                                                                      bytesPerRow:width*4
                                                                     bitsPerPixel:4*8];
    [[sceneKitView openGLContext] makeCurrentContext];
    glReadPixels(0, 0, (int)width, (int)height, GL_RGBA, GL_UNSIGNED_BYTE, [imageRep bitmapData]);
    [NSOpenGLContext clearCurrentContext];
    NSImage* outputImage = [[NSImage alloc] initWithSize:NSMakeSize(width, height)];
    [outputImage addRepresentation:imageRep];
    NSImage* flippedImage = [NSImage imageWithSize:NSMakeSize(width, height) flipped:YES drawingHandler:^BOOL(NSRect dstRect) {
        [imageRep drawInRect:dstRect];
        return YES;
    }];
    return flippedImage;
}

不要忘记链接OpenGL.framework和#import "OpenGL/gl.h"

<强>更新
SceneKit似乎使用翻转的上下文。我添加了一些代码来修复颠倒的图像。

更新2
更新了代码以考虑支持比例因子（用于视网膜显示）

Answer 2

在OS X v10.10和iOS 8中，SCNView添加了snapshot方法，因此您可以获得NSImage（或UIImage）更多内容容易。

Answer 3

我用SCNRenderer编写了代码，因此它不依赖于屏幕内容。

public extension SCNRenderer {

    public func renderToImageSize(size: CGSize, floatComponents: Bool, atTime time: NSTimeInterval) -> CGImage? {

        var thumbnailCGImage: CGImage?

        let width = GLsizei(size.width), height = GLsizei(size.height)
        let samplesPerPixel = 4

        #if os(iOS)
            let oldGLContext = EAGLContext.currentContext()
            let glContext = unsafeBitCast(context, EAGLContext.self)

            EAGLContext.setCurrentContext(glContext)
            objc_sync_enter(glContext)
        #elseif os(OSX)
            let oldGLContext = CGLGetCurrentContext()
            let glContext = unsafeBitCast(context, CGLContextObj.self)

            CGLSetCurrentContext(glContext)
            CGLLockContext(glContext)
        #endif

        // set up the OpenGL buffers
        var thumbnailFramebuffer: GLuint = 0
        glGenFramebuffers(1, &thumbnailFramebuffer)
        glBindFramebuffer(GLenum(GL_FRAMEBUFFER), thumbnailFramebuffer); checkGLErrors()

        var colorRenderbuffer: GLuint = 0
        glGenRenderbuffers(1, &colorRenderbuffer)
        glBindRenderbuffer(GLenum(GL_RENDERBUFFER), colorRenderbuffer)
        if floatComponents {
            glRenderbufferStorage(GLenum(GL_RENDERBUFFER), GLenum(GL_RGBA16F), width, height)
        } else {
            glRenderbufferStorage(GLenum(GL_RENDERBUFFER), GLenum(GL_RGBA8), width, height)
        }
        glFramebufferRenderbuffer(GLenum(GL_FRAMEBUFFER), GLenum(GL_COLOR_ATTACHMENT0), GLenum(GL_RENDERBUFFER), colorRenderbuffer); checkGLErrors()

        var depthRenderbuffer: GLuint = 0
        glGenRenderbuffers(1, &depthRenderbuffer)
        glBindRenderbuffer(GLenum(GL_RENDERBUFFER), depthRenderbuffer)
        glRenderbufferStorage(GLenum(GL_RENDERBUFFER), GLenum(GL_DEPTH_COMPONENT24), width, height)
        glFramebufferRenderbuffer(GLenum(GL_FRAMEBUFFER), GLenum(GL_DEPTH_ATTACHMENT), GLenum(GL_RENDERBUFFER), depthRenderbuffer); checkGLErrors()

        let framebufferStatus = Int32(glCheckFramebufferStatus(GLenum(GL_FRAMEBUFFER)))
        assert(framebufferStatus == GL_FRAMEBUFFER_COMPLETE)
        if framebufferStatus != GL_FRAMEBUFFER_COMPLETE {
            return nil
        }

        // clear buffer
        glViewport(0, 0, width, height)
        glClear(GLbitfield(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT)); checkGLErrors()

        // render
        renderAtTime(time); checkGLErrors()

        // create the image
        if floatComponents { // float components (16-bits of actual precision)

            // slurp bytes out of OpenGL
            typealias ComponentType = Float

            var imageRawBuffer = [ComponentType](count: Int(width * height) * samplesPerPixel * sizeof(ComponentType), repeatedValue: 0)
            glReadPixels(GLint(0), GLint(0), width, height, GLenum(GL_RGBA), GLenum(GL_FLOAT), &imageRawBuffer)

            // flip image vertically — OpenGL has a different 'up' than CoreGraphics
            let rowLength = Int(width) * samplesPerPixel
            for rowIndex in 0..<(Int(height) / 2) {
                let baseIndex = rowIndex * rowLength
                let destinationIndex = (Int(height) - 1 - rowIndex) * rowLength

                swap(&imageRawBuffer[baseIndex..<(baseIndex + rowLength)], &imageRawBuffer[destinationIndex..<(destinationIndex + rowLength)])
            }

            // make the CGImage
            var imageBuffer = vImage_Buffer(
                data: UnsafeMutablePointer<Float>(imageRawBuffer),
                height: vImagePixelCount(height),
                width: vImagePixelCount(width),
                rowBytes: Int(width) * sizeof(ComponentType) * samplesPerPixel)

            var format = vImage_CGImageFormat(
                bitsPerComponent: UInt32(sizeof(ComponentType) * 8),
                bitsPerPixel: UInt32(sizeof(ComponentType) * samplesPerPixel * 8),
                colorSpace: nil, // defaults to sRGB
                bitmapInfo: CGBitmapInfo(CGImageAlphaInfo.PremultipliedLast.rawValue | CGBitmapInfo.ByteOrder32Little.rawValue | CGBitmapInfo.FloatComponents.rawValue),
                version: UInt32(0),
                decode: nil,
                renderingIntent: kCGRenderingIntentDefault)

            var error: vImage_Error = 0
            thumbnailCGImage = vImageCreateCGImageFromBuffer(&imageBuffer, &format, nil, nil, vImage_Flags(kvImagePrintDiagnosticsToConsole), &error)!.takeRetainedValue()

        } else { // byte components

            // slurp bytes out of OpenGL
            typealias ComponentType = UInt8

            var imageRawBuffer = [ComponentType](count: Int(width * height) * samplesPerPixel * sizeof(ComponentType), repeatedValue: 0)
            glReadPixels(GLint(0), GLint(0), width, height, GLenum(GL_RGBA), GLenum(GL_UNSIGNED_BYTE), &imageRawBuffer)

            // flip image vertically — OpenGL has a different 'up' than CoreGraphics
            let rowLength = Int(width) * samplesPerPixel
            for rowIndex in 0..<(Int(height) / 2) {
                let baseIndex = rowIndex * rowLength
                let destinationIndex = (Int(height) - 1 - rowIndex) * rowLength

                swap(&imageRawBuffer[baseIndex..<(baseIndex + rowLength)], &imageRawBuffer[destinationIndex..<(destinationIndex + rowLength)])
            }

            // make the CGImage
            var imageBuffer = vImage_Buffer(
                data: UnsafeMutablePointer<Float>(imageRawBuffer),
                height: vImagePixelCount(height),
                width: vImagePixelCount(width),
                rowBytes: Int(width) * sizeof(ComponentType) * samplesPerPixel)

            var format = vImage_CGImageFormat(
                bitsPerComponent: UInt32(sizeof(ComponentType) * 8),
                bitsPerPixel: UInt32(sizeof(ComponentType) * samplesPerPixel * 8),
                colorSpace: nil, // defaults to sRGB
                bitmapInfo: CGBitmapInfo(CGImageAlphaInfo.PremultipliedLast.rawValue | CGBitmapInfo.ByteOrder32Big.rawValue),
                version: UInt32(0),
                decode: nil,
                renderingIntent: kCGRenderingIntentDefault)

            var error: vImage_Error = 0
            thumbnailCGImage = vImageCreateCGImageFromBuffer(&imageBuffer, &format, nil, nil, vImage_Flags(kvImagePrintDiagnosticsToConsole), &error)!.takeRetainedValue()
        }

        #if os(iOS)
            objc_sync_exit(glContext)
            if oldGLContext != nil {
                EAGLContext.setCurrentContext(oldGLContext)
            }
        #elseif os(OSX)
            CGLUnlockContext(glContext)
            if oldGLContext != nil {
                CGLSetCurrentContext(oldGLContext)
            }
        #endif

        return thumbnailCGImage
    }
}


func checkGLErrors() {
    var glError: GLenum
    var hadError = false
    do {
        glError = glGetError()
        if glError != 0 {
            println(String(format: "OpenGL error %#x", glError))
            hadError = true
        }
    } while glError != 0
    assert(!hadError)
}

无法创建SCNView的屏幕截图

3 个答案: