I have an app that lets people combine up to 4 pictures. However when I let them choose from their photos (up to 4) it can be very slow even when I set image quality to FastFormat. It will take 4 seconds (about 1 second per photo). On highest quality, 4 images takes 6 seconds.
Can you suggest anyway I get get the images out faster?
Here is the block where I process images.
func processImages()
{
_selectediImages = Array()
_cacheImageComplete = 0
for asset in _selectedAssets
{
var options:PHImageRequestOptions = PHImageRequestOptions()
options.synchronous = true
options.deliveryMode = PHImageRequestOptionsDeliveryMode.FastFormat
PHImageManager.defaultManager().requestImageForAsset(asset, targetSize:CGSizeMake(CGFloat(asset.pixelWidth), CGFloat(asset.pixelHeight)), contentMode: .AspectFit, options: options)
{
result, info in
var minRatio:CGFloat = 1
//Reduce file size so take 1/3 the screen w&h
if(CGFloat(asset.pixelWidth) > UIScreen.mainScreen().bounds.width/2 || CGFloat(asset.pixelHeight) > UIScreen.mainScreen().bounds.height/2)
{
minRatio = min((UIScreen.mainScreen().bounds.width/2)/(CGFloat(asset.pixelWidth)), ((UIScreen.mainScreen().bounds.height/2)/CGFloat(asset.pixelHeight)))
}
var size:CGSize = CGSizeMake((CGFloat(asset.pixelWidth)*minRatio),(CGFloat(asset.pixelHeight)*minRatio))
UIGraphicsBeginImageContextWithOptions(size, false, 0.0)
result.drawInRect(CGRectMake(0, 0, size.width, size.height))
var final = UIGraphicsGetImageFromCurrentImageContext()
var image = iImage(uiimage: final)
self._selectediImages.append(image)
self._cacheImageComplete!++
println(self._cacheImageComplete)
if(self._cacheImageComplete == self._selectionCount)
{
self._processingImages = false
self.selectionCallback(self._selectediImages)
}
}
}
}
Don't resize the images yourself — part of what PHImageManager
is for is to do that for you. (It also caches the thumbnail images so that you can get them more quickly next time, and shares that cache across apps so that you don't end up with half a dozen apps creating half a dozen separate 500MB thumbnail caches of your whole library.)
func processImages() {
_selectediImages = Array()
_cacheImageComplete = 0
for asset in _selectedAssets {
let options = PHImageRequestOptions()
options.deliveryMode = .FastFormat
// request images no bigger than 1/3 the screen width
let maxDimension = UIScreen.mainScreen().bounds.width / 3 * UIScreen.mainScreen().scale
let size = CGSize(width: maxDimension, height: maxDimension)
PHImageManager.defaultManager().requestImageForAsset(asset, targetSize: size, contentMode: .AspectFill, options: options)
{ result, info in
// probably some of this code is unnecessary, too,
// but I'm not sure what you're doing here so leaving it alone
self._selectediImages.append(result)
self._cacheImageComplete!++
println(self._cacheImageComplete)
if self._cacheImageComplete == self._selectionCount {
self._processingImages = false
self.selectionCallback(self._selectediImages)
}
}
}
}
}
Notable changes:
requestImageForAsset
and use the AspectFill
mode. This will get you an image that crops to fill that square no matter what its aspect ratio is.FastFormat
, so you might get blurry images anyway.)