旋转UIImage单点触控

Question

我正在尝试从手机上传图像到我的web服务，但我注意到当我上传图像时图像方向丢失。上传之前是否需要做些什么来确保图片的上传方向正确？

我还查看了其他地方，发现objective-C代码可以旋转我转换为C#的图像，但每次使用Rotate方法时，图像都会变黑，即我猜没有显示任何内容。

我附上我的代码供你参考，如果有人能告诉我我做错了什么，我会非常，非常感谢。谢谢!

    public static UIImage RotateImage(this UIImage image)
    {
        UIImage imageToReturn = null;
        if(image.Orientation == UIImageOrientation.Up)
        {
            imageToReturn = image;
        }
        else 
        {
            CGAffineTransform transform = CGAffineTransform.MakeIdentity();

            switch (image.Orientation) {
                case UIImageOrientation.Down:
                case UIImageOrientation.DownMirrored:
                    transform.Translate(image.Size.Width, image.Size.Height);
                    transform.Rotate((float)Math.PI);
                    break;

                case UIImageOrientation.Left:
                case UIImageOrientation.LeftMirrored:
                    transform.Translate(image.Size.Width, 0);
                    transform.Rotate((float)Math.PI/2);
                    break;

                case UIImageOrientation.Right:
                case UIImageOrientation.RightMirrored:
                    transform.Translate(0, image.Size.Height);
                    transform.Rotate((float)-Math.PI/2);
                    break;
                case UIImageOrientation.Up:
                case UIImageOrientation.UpMirrored:
                    break;
            }

            switch (image.Orientation) {
                case UIImageOrientation.UpMirrored:
                case UIImageOrientation.DownMirrored:
                    transform.Translate(image.Size.Width, 0);
                    transform.Scale(-1, 1);
                    break;

                case UIImageOrientation.LeftMirrored:
                case UIImageOrientation.RightMirrored:
                    transform.Translate(image.Size.Height, 0);
                    transform.Scale(-1, 1);
                    break;
                case UIImageOrientation.Up:
                case UIImageOrientation.Down:
                case UIImageOrientation.Left:
                case UIImageOrientation.Right:
                    break;
            }

            //now draw image
            using(var context = new CGBitmapContext(IntPtr.Zero,
                                                    (int)image.Size.Width, 
                                                    (int)image.Size.Height, 
                                                    image.CGImage.BitsPerComponent,
                                                    image.CGImage.BytesPerRow,
                                                    image.CGImage.ColorSpace,
                                                    image.CGImage.BitmapInfo)){
                context.ConcatCTM(transform);
                switch (image.Orientation) 
                {
                    case UIImageOrientation.Left:
                    case UIImageOrientation.LeftMirrored:
                    case UIImageOrientation.Right:
                    case UIImageOrientation.RightMirrored:
                        // Grr...
                        context.DrawImage(new RectangleF(PointF.Empty,new SizeF(image.Size.Height, image.Size.Width)), image.CGImage);
                        break;
                    default:
                        context.DrawImage(new RectangleF(PointF.Empty, new SizeF(image.Size.Width, image.Size.Height)), image.CGImage);
                        break;
                }

                using(var imageRef = context.ToImage())
                {
                    imageToReturn = new UIImage(imageRef);
                }
            }
        }

        return imageToReturn;
    }

Answer 1

你得到黑色图像的原因是平移和旋转调用是向后的。iPod/iphone上的正常肖像图片都是“正确”的。转换它们的正确代码使用：

        case UIImageOrientation.Right:
        case UIImageOrientation.RightMirrored:
            transform.Rotate (-(float)Math.PI / 2);
            transform.Translate (0, input.Size.Height);
            break;

变换函数依赖于顺序。这段代码将它旋转到正确的方向，但由于旋转大约是左下角的0,0坐标，图像现在正好离开框架的底部。然后，翻译将它推到它所属的位置。

原始代码会将图像侧向推离框架的顶部，然后旋转会使图像向右转，但会远远偏离框架的右侧。

使用一个较小的高度值，例如100或200和pi/4，可以很容易地显示出更改这些函数的顺序时得到的差异，因为一些原始图像将始终可见。

Answer 2

使用@Random提供的信息，我更正了原始代码，使其正常工作：

    private byte[] RotateImage(UIImage image)
    {
        UIImage imageToReturn = null;
        if (image.Orientation == UIImageOrientation.Up)
        {
            imageToReturn = image;
        }
        else
        {
            CGAffineTransform transform = CGAffineTransform.MakeIdentity();

            switch (image.Orientation)
            {
                case UIImageOrientation.Down:
                case UIImageOrientation.DownMirrored:
                    transform.Rotate((float)Math.PI);
                    transform.Translate(image.Size.Width, image.Size.Height);
                    break;

                case UIImageOrientation.Left:
                case UIImageOrientation.LeftMirrored:
                    transform.Rotate((float)Math.PI / 2);
                    transform.Translate(image.Size.Width, 0);
                    break;

                case UIImageOrientation.Right:
                case UIImageOrientation.RightMirrored:
                    transform.Rotate(-(float)Math.PI / 2);
                    transform.Translate(0, image.Size.Height);
                    break;
                case UIImageOrientation.Up:
                case UIImageOrientation.UpMirrored:
                    break;
            }

            switch (image.Orientation)
            {
                case UIImageOrientation.UpMirrored:
                case UIImageOrientation.DownMirrored:
                    transform.Translate(image.Size.Width, 0);
                    transform.Scale(-1, 1);
                    break;

                case UIImageOrientation.LeftMirrored:
                case UIImageOrientation.RightMirrored:
                    transform.Translate(image.Size.Height, 0);
                    transform.Scale(-1, 1);
                    break;
                case UIImageOrientation.Up:
                case UIImageOrientation.Down:
                case UIImageOrientation.Left:
                case UIImageOrientation.Right:
                    break;
            }

            //now draw image
            using (var context = new CGBitmapContext(IntPtr.Zero,
                                                    (int)image.Size.Width,
                                                    (int)image.Size.Height,
                                                    image.CGImage.BitsPerComponent,
                                                    image.CGImage.BytesPerRow,
                                                    image.CGImage.ColorSpace,
                                                    image.CGImage.BitmapInfo))
            {
                context.ConcatCTM(transform);
                switch (image.Orientation)
                {
                    case UIImageOrientation.Left:
                    case UIImageOrientation.LeftMirrored:
                    case UIImageOrientation.Right:
                    case UIImageOrientation.RightMirrored:
                        // Grr...
                        context.DrawImage(new RectangleF(PointF.Empty, new SizeF((float)image.Size.Height, (float)image.Size.Width)), image.CGImage);
                        break;
                    default:
                        context.DrawImage(new RectangleF(PointF.Empty, new SizeF((float)image.Size.Width, (float)image.Size.Height)), image.CGImage);
                        break;
                }

                using (var imageRef = context.ToImage())
                {
                    imageToReturn = new UIImage(imageRef);
                }
            }
        }

        using (NSData imageData = imageToReturn.AsJPEG())
        {
            Byte[] byteArray = new Byte[imageData.Length];
            System.Runtime.InteropServices.Marshal.Copy(imageData.Bytes, byteArray, 0, Convert.ToInt32(imageData.Length));
            return byteArray;
        }
    }

一段非常有用的代码

Answer 3

我通过this question找到了this gist。希望这段代码能为你工作！