ios - 如何将过滤后的图像保存在数组中？

Question

我有一个 UICollectionView(水平)，并在单元格中放置了应用了滤镜的图像。

我这样做了:

var filtered = [Int: UIImage]()
func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {
    let cell = collectionView.dequeueReusableCellWithReuseIdentifier("filterCell", forIndexPath: indexPath) as! filterCell

    let op1 = NSBlockOperation { () -> Void in
        let img = self.image!
        let img1 = self.applyFilterTo(img, filter: self.filtersImages[indexPath.row])

        NSOperationQueue.mainQueue().addOperationWithBlock({ () -> Void in

            if let filtered = self.filtered[indexPath.row] {
                cell.imageView.image = self.filtered[indexPath.row]
            } else {
                self.filtered[indexPath.row] = img1
                cell.imageView.image = self.filtered[indexPath.row]

            }
        })
    }

    self.queue!.addOperation(op1);

    return cell
}

地点:

var myFilter = CIFilter()
func applyFilterTo(image: UIImage, filter: String) -> UIImage {
    let sourceImage = CIImage(image: image)

    myFilter = CIFilter(name: filter)!
    myFilter.setDefaults()

    myFilter.setValue(sourceImage, forKey: kCIInputImageKey)

    let context = CIContext(options: nil)

    let outputCGImage = context.createCGImage(myFilter.outputImage!, fromRect: myFilter.outputImage!.extent)

    let newImage = UIImage(CGImage: outputCGImage, scale: image.scale, orientation: image.imageOrientation)

    return newImage
}

所以这里的原则是将我的过滤器应用于图像，将其保存在我的字典中，然后从字典中滚动加载图像。但它仍然会拍摄图像，应用滤镜，然后再显示。因此，滚动时我的 UICollectionView 卡住，图像上的过滤器发生变化。

我做错了什么以及如何解决这个问题？

Answer 1

如果图像已在 self.filtered[indexPath.row] 中，为什么需要执行 let img1 = self.applyFilterTo(img, filter: self.filtersImages[indexPath.row]) ？

所以我认为你应该检查if letfiltered = self.filtered[indexPath.row] {，如果没有，就开始过滤它。

对于您的代码，它将是这样的:

func collectionView(collectionView: UICollectionView, cellForItemAtIndexPath indexPath: NSIndexPath) -> UICollectionViewCell {
    let cell = collectionView.dequeueReusableCellWithReuseIdentifier("filterCell", forIndexPath: indexPath) as! filterCell

    if let filtered = self.filtered[indexPath.row] {
      cell.imageView.image = filtered
    } else {
      let op1 = NSBlockOperation { () -> Void in
        let img = self.image!
        let img1 = self.applyFilterTo(img, filter: self.filtersImages[indexPath.row])

        NSOperationQueue.mainQueue().addOperationWithBlock({ () -> Void in
          self.filtered[indexPath.row] = img1
          cell.imageView.image = self.filtered[indexPath.row]
        })
      }

      self.queue!.addOperation(op1);
    }

  return cell
}