问题描述
我的gif生成器功能降低了分辨率并使一系列照片中的帧最小化，但是我没有什么可以减少颜色数量或使其有损的.我将如何在Swift 4中做到这一点?
My gif generator function reduces the resolution and minimizes the frames from a series of photos, but I don't have anything to reduce the amount of colors or make it lossy. How would I go about doing this in Swift 4?
func generateGif(photos: [UIImage], filename: String) -> Bool {
let documentsDirectoryPath = NSSearchPathForDirectoriesInDomains(.documentDirectory, .userDomainMask, true)[0]
let path = documentsDirectoryPath.appending(filename)
let fileProperties = [kCGImagePropertyGIFDictionary as String: [kCGImagePropertyGIFLoopCount as String: 0]]
let gifProperties = [kCGImagePropertyGIFDictionary as String: [kCGImagePropertyGIFDelayTime as String: 0.1]] // actual speed is 0.2
let cfURL = URL(fileURLWithPath: path) as CFURL
if let destination = CGImageDestinationCreateWithURL(cfURL, kUTTypeGIF, photos.count, nil) {
CGImageDestinationSetProperties(destination, fileProperties as CFDictionary?)
var inc:Int = 0
for _ in 0..<15 { // actual photos.count is 31
let photo = photos[inc]
var width:CGFloat = photo.size.width
var height:CGFloat = photo.size.height
let maxWidthHeight:CGFloat = 500
if(photo.size.width > maxWidthHeight || photo.size.height > maxWidthHeight){ // gif beyond max width or height
if(photo.size.width > photo.size.height){
width = maxWidthHeight
let percentChange = width / photo.size.width
height = photo.size.height * percentChange
}else{
height = maxWidthHeight
let percentChange = height / photo.size.height
width = photo.size.width * percentChange
}
print("w:\(width) h:\(height) inc:\(inc)")
}
let smallerPhoto = imageWithImage(image:photo, scaledToSize:CGSize(width:width, height:height))
CGImageDestinationAddImage(destination, smallerPhoto.cgImage!, gifProperties as CFDictionary?)
inc+=2 // skipping ahead incrementation for less frames
}
// here it's saving to a photo album when it's done and reporting the filesize
CustomPhotoAlbum.sharedInstance.savePhoto(URL: URL(fileURLWithPath: path), completion: {
var fileSize : UInt64
do {
let attr = try FileManager.default.attributesOfItem(atPath: path)
fileSize = attr[FileAttributeKey.size] as! UInt64
print("gif is \(fileSize/1000000) megabytes")
} catch {
print("Error: \(error)")
}
})
return CGImageDestinationFinalize(destination)
}
return false
}
任何宽度或高度超过500的文件都会返回大约11兆字节的文件.我想它可能会小得多.
Anything above 500 width or height returns a file that is around 11 megabytes. I imagine it could be far smaller.
推荐答案
在gifsicle 签出 giflossy /kornelski/giflossy"rel =" nofollow noreferrer> github .它确实可以满足您的需求，而且功能更多.它在C语言中，但您可以从中获得一些启发，并迅速移植相关部分.
Check out giflossy based ongifsicle on github. It does exactly what you want and more. It’s in C but you can get some inspiration from there and port the relevant parts to swift.
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