Currently I'm working on downloading all the image's provided within a user's selected folder. So this process consists of:
- Requesting all the thumbnails of the images
- Requesting all the original images
- Take the original and create a retina compressed version to display
The reason we need to keep the original is because that's the file we will be printing on anything from 8x10 picture frames to 40x40 canvas wraps, so having the original is important. The only part that's causing the crash is taking the original and creating the compressed version. I ended up using this:
autoreleasepool({
self.compressed = self.saveImageWithReturn(image:self.original!.scaledImage(newSize: 2048), type: .Compressed)
})
scaling the image by calling:
func scaledImage(newSize newHeight : CGFloat) -> UIImage {
let scale = newHeight / size.height
let newWidth = size.width * scale
UIGraphicsBeginImageContext(CGSizeMake(newWidth, newHeight))
drawInRect(CGRectMake(0, 0, newWidth, newHeight))
let newImage = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()
return newImage
}
which saves the image to the device documents by using this:
private func saveImageWithReturn(image img: UIImage, type: PhotoType) -> UIImage? {
guard let path = ASSET_PATH.URLByAppendingPathComponent(type.rawValue).path,
let imageData = UIImageJPEGRepresentation(img, type.compression())
else { return nil }
imageData.writeToFile(path, atomically: true)
return UIImage(data: imageData)
}
The autoreleasepool actually fixes the problem of it crashing, but it's operating on the main thread basically freezing all user interaction. Then I tried
dispatch_async(dispatch_get_global_queue(QOS_CLASS_USER_INITIATED, 0), {
autoreleasepool({
self.compressed = self.saveImageWithReturn(image: self.original!.scaledImage(newSize: 2048), type: .Compressed)
})
})
and it results in it not properly releasing memory quick enough and it crashes. The reason I believe this is happening because it's not processing the scaledImage(newSize: 2048) quick enough causing the multiple requests to stack and all try to process this and having multiple instances all trying to hold onto an original image will result in memory warnings or a crash from it. So far I know it works perfectly on the iPad Air 2, but the iPad Generation 4 seems to process it slow.
Not sure if this is the best way of doing things, or if I should be finding another way to scale and compress the original file. Any help would be really appreciated.
