Question

我目前正在使用CGContextDrawImage旋转图像，但无论何时调用它都会有一个巨大的内存峰值。较新的设备可以处理它，但是具有较低内存的设备（例如iPhone 4s）则不能。该图像是用户在AVCaptureSessionPresetHigh

处拍摄的大文件

我目前正在使用此扩展程序将图片旋转到UIImage

func rotate(orientation: UIImageOrientation) -> UIImage{
    if(orientation == UIImageOrientation.Up){return self}

    var transform: CGAffineTransform = CGAffineTransformIdentity

    if(orientation == UIImageOrientation.Down || orientation == UIImageOrientation.DownMirrored){
        transform = CGAffineTransformTranslate(transform, self.size.width, self.size.height)
        transform = CGAffineTransformRotate(transform, CGFloat(M_PI))
    }
    else if(orientation == UIImageOrientation.Left || orientation == UIImageOrientation.LeftMirrored){
        transform = CGAffineTransformTranslate(transform, self.size.width, 0)
        transform = CGAffineTransformRotate(transform, CGFloat(M_PI_2))
    }
    else if(orientation == UIImageOrientation.Right || orientation == UIImageOrientation.RightMirrored){
        transform = CGAffineTransformTranslate(transform, 0, self.size.height)
        transform = CGAffineTransformRotate(transform,  CGFloat(-M_PI_2))
    }


    if(orientation == UIImageOrientation.UpMirrored || orientation == UIImageOrientation.DownMirrored){
        transform = CGAffineTransformTranslate(transform, self.size.width, 0)
        transform = CGAffineTransformScale(transform, -1, 1)
    }
    else if(orientation == UIImageOrientation.LeftMirrored || orientation == UIImageOrientation.RightMirrored){
        transform = CGAffineTransformTranslate(transform, self.size.height, 0)
        transform = CGAffineTransformScale(transform, -1, 1);
    }

    let ref: CGContextRef = CGBitmapContextCreate(nil, Int(self.size.width), Int(self.size.height), CGImageGetBitsPerComponent(self.CGImage), 0, CGImageGetColorSpace(self.CGImage), CGImageGetBitmapInfo(self.CGImage))
    CGContextConcatCTM(ref, transform)

    if(orientation == UIImageOrientation.Left || orientation == UIImageOrientation.LeftMirrored || orientation == UIImageOrientation.Right || orientation == UIImageOrientation.RightMirrored){
        CGContextDrawImage(ref, CGRectMake(0, 0, self.size.height, self.size.width), self.CGImage)
    }
    else{
        CGContextDrawImage(ref, CGRectMake(0, 0, self.size.width, self.size.height), self.CGImage)
    }


    let cgImg: CGImageRef = CGBitmapContextCreateImage(ref)
    let rotated: UIImage = UIImage(CGImage: cgImg)!

    return rotated
}

此代码适用于iPhone 5和6等设备，但由于内存不足，几乎总会导致iPhone 4s崩溃。

我知道我可以使用指定方向的EXIF数据上传图像，但我觉得只需在上传之前旋转图像就可以防止出现进一步的问题。

iOS如何使用EXIF数据旋转图像以进行显示？例如，虽然使用

UIImage(image.CGImage, scale: 1.0, orientation: UIImageOrientation.Right)

更改EXIF数据，图像仍然以正确的方向显示在屏幕上，对内存的影响要小得多。是否有一些真正的低级代码可以通过像上面的代码一样使用GPU来实现这个目的呢？

我还想在上传之前避免缩小图像。

有什么方法可以减少旋转图像的影响，例如将其旋转成碎片，还是我必须找到替代品？

在没有内存峰值的情况下旋转UIImage

0 个答案: