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我正在使用图像视图并根据滑块值将亮度效果应用于图像视图的图像。滑块值范围从 -100 到 +100。在连续移动滑块时，应用程序会关闭。我什至尝试过处理上下文但同样的问题存在。请参考以下代码并帮助我解决。

    UIImageView imageView;
    private float brightnessAmount;
    private bool isBrightnessApplied;
    private ImageEffect effects;
    private CIContext filterContext;
    UIImage originalImage;

    public override void ViewDidLoad()
    {
        base.ViewDidLoad();

        
        effects = ImageEffect.Brightness;
        originalImage = UIImage.FromBundle("image.jpg");

        var frame = this.View.Frame;

        UIView mainView = new UIView();
        mainView.Frame = frame;

        imageView = new UIImageView();
        imageView.Frame = new CGRect(frame.Left, frame.Top, frame.Width, frame.Height - 100);
        imageView.Image = UIImage.FromBundle("image.jpg");
        mainView.Add(imageView);

        UISlider slider = new UISlider();
        slider.Frame = new CGRect(frame.Left, imageView.Frame.Bottom, frame.Width, 100);
        slider.MinValue = -100;
        slider.MaxValue = 100;
        slider.ValueChanged += Slider_ValueChanged;
        mainView.Add(slider);
        this.Add(mainView);
    }

   private void Slider_ValueChanged(object sender, EventArgs e)
    {
        var amount = (sender as UISlider).Value;

        amount = amount > 100 ? 100 : amount < -100 ? -100 : amount;
       
        amount = amount / 100;
        CIImage currentImage = GetFilteredCIImage(effects);
        CIColorControls colorCtrls = new CIColorControls() { Image = currentImage };
        if (effects == ImageEffect.Brightness)
        {
            colorCtrls.Brightness = amount;
            brightnessAmount = amount;
            isBrightnessApplied = true;
        }
       
        if (filterContext == null )
            filterContext = CIContext.FromOptions(null);
        var outputImage = colorCtrls.OutputImage;
        var result = filterContext.CreateCGImage(outputImage, outputImage.Extent);
        filterContext.ClearCaches();
     
        imageView.Image = UIImage.FromImage(result);
        result.Dispose();
        result = null;
        outputImage.Dispose();
        outputImage = null;
    }

    private CIImage GetFilteredCIImage(ImageEffect effect)
    {
        CIImage currentImage = CIImage.FromCGImage(originalImage.CGImage);
        if (effect == ImageEffect.None) return currentImage;
       
        if ( isBrightnessApplied)
        {
            CIColorControls colorCtrls = new CIColorControls() { Image = currentImage };
            colorCtrls.Brightness = brightnessAmount;
            currentImage = colorCtrls.OutputImage;
            colorCtrls.Dispose();
        }
        return currentImage;
    }
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1 回答 1

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如果你想改变 Image 的亮度，检查下面的代码。

注意：您需要在真实设备上对其进行测试，因为它使用 GPU 上下文。在模拟器上会有延迟。

using CoreGraphics;
using CoreImage;
using Foundation;
using System;
using UIKit;
using OpenGLES;
using System.Threading.Tasks;

namespace App10
{
    public partial class ViewController : UIViewController
    {


        UIImageView imageView;
        CIContext context;
        UIImage originalImage;

        CIColorControls colorCtrls;
        bool isbusy;
        public ViewController (IntPtr handle) : base (handle)
        {
        }

        public override void ViewDidLoad()
        {
            base.ViewDidLoad();

            originalImage = UIImage.FromBundle("Images.png");

            var frame = this.View.Frame;

            UIView mainView = new UIView();
            mainView.Frame = frame;

            imageView = new UIImageView();
            imageView.Frame = new CGRect(frame.Left, frame.Top, frame.Width, frame.Height - 100);
            imageView.Image = UIImage.FromBundle("Images.png");
            mainView.Add(imageView);

            UISlider slider = new UISlider();
            slider.Frame = new CGRect(frame.Left, imageView.Frame.Bottom, frame.Width, 100);
            slider.MinValue = -100;
            slider.MaxValue = 100;
            slider.ValueChanged += Slider_TouchUpInside; 
            mainView.Add(slider);
            this.Add(mainView);


            colorCtrls = new CIColorControls();
            colorCtrls.InputImage = new CIImage(originalImage);

            // Create the context only once, and re-use it
            var contextOptions = new CIContextOptions();
            contextOptions.UseSoftwareRenderer = false; // gpu vs. cpu
                                                        // On save of the image, create a new context with highqual attributes and re-apply the filter... 
            contextOptions.HighQualityDownsample = false;
            contextOptions.PriorityRequestLow = false; // high queue order it
            contextOptions.CIImageFormat = (int)CIFormat.ARGB8; // use 32bpp, vs. 64|128bpp 
            context = CIContext.FromOptions(contextOptions);


            // Perform any additional setup after loading the view, typically from a nib.
        }

        private async void Slider_TouchUpInside(object sender, EventArgs e)
        {
            if(!isbusy)
            {
                isbusy = true;
                var slider = sender as UISlider;
                imageView.Image = await FilterImageAsync(slider.Value / 100);
                isbusy = false;
            }
        }


      
        async Task<UIImage> FilterImageAsync(float value)
        {  

             var transformImage = new Func<UIImage>(() => {
                    colorCtrls.Brightness = value;
                    CIImage input = new CIImage(originalImage);
                    var output = colorCtrls.OutputImage;
                    var cgImage = context.CreateCGImage(output, input.Extent);
                    var filteredImage = new UIImage(cgImage);
                    return filteredImage;
                });
          
            
            UIImage image = await Task.Run<UIImage>(transformImage);
            return image;
        }
    }
}
于 2021-01-25T09:24:23.680 回答