這里只講ImageIO中CGImageSource常見的三種使用方式，一種是進行圖片格式解碼讀取(包括原始圖片和生成縮略圖)，另一種是獲取圖片的相關信息(如：定位，拍攝設備，分辨率等)，最后一種是漸進式加載。
基本知識
CGImageSource:解碼-讀取圖片數據類
//查看支持解碼的type類型
let mySourceTypes : CFArray = CGImageSourceCopyTypeIdentifiers();
print(mySourceTypes);
ps.支持格式過多，我刪了一部分日志
(
"public.jpeg",
"public.png",
"com.compuserve.gif",
"com.canon.tif-raw-image",
"com.adobe.raw-image",
"com.dxo.raw-image",
"com.konicaminolta.raw-image",
"com.olympus.sr-raw-image",
"com.microsoft.ico",
"com.microsoft.bmp",
...
"com.apple.icns",
"com.adobe.photoshop-image",
"com.microsoft.cur",
"com.truevision.tga-image",
"com.ilm.openexr-image",
"org.webmproject.webp",
"public.radiance",
"public.pbm",
"public.mpo-image",
"public.pvr",
"com.microsoft.dds"
)
CGImageDestination:編碼-寫入數據類，寫入數據類放在另一篇文章中
//查看支持編碼的type類型
let myDestinationTypes : CFArray = CGImageDestinationCopyTypeIdentifiers();
print(myDestinationTypes);
ImageSourceOption 鍵值
kCGImageSourceTypeIdentifierHint：設置預設的圖片格式，格式參照UTType.h
kCGImageSourceShouldAllowFloat：如果文件格式支持，是否應將圖像作為浮點CGImageRef返回
kCGImageSourceShouldCache：是否應以解碼形式緩存圖像
kCGImageSourceCreateThumbnailFromImageIfAbsent：如果原圖中縮略圖不存在，是否根據原圖創(chuàng)建縮略圖
kCGImageSourceCreateThumbnailFromImageAlways：是否始終根據原圖創(chuàng)建縮略圖，即使原圖中存在縮略圖
kCGImageSourceThumbnailMaxPixelSize：縮略圖最大尺寸，CFNumber格式
kCGImageSourceCreateThumbnailWithTransform：縮略圖是否根據原圖像的方向和像素縱橫比進行旋轉和縮放
一.導入圖片數據，進行圖片格式解碼
正如前文基礎知識中CGImageSource支持解碼的圖片數據類型，是不是除了png,jpg很多格式都沒見過。有一些格式圖片沒有辦法通過UIImage(named:String)來進行加載，這里就需要通過CGImageSource進行格式轉換成CGImage進行加載
func createImageFromSource()-> CGImage?{
let myOptions = [kCGImageSourceShouldCache : kCFBooleanTrue,kCGImageSourceShouldAllowFloat : kCFBooleanTrue] as CFDictionary;
//這里我放了一張png圖片在工程中
guard let imgPath = Bundle.main.path(forResource: "IMG_0868", ofType: ".PNG")else{
return nil
}
guard let myImageSource = CGImageSourceCreateWithURL(URL(fileURLWithPath: imgPath) as CFURL, myOptions) else {
print(stderr, "Image source is NULL.");
return nil
}
//通過CGImageSourceCreateImageAtIndex函數生成cgimage格式數據
guard let myImage = CGImageSourceCreateImageAtIndex(myImageSource,0,nil)else {
print(stderr, "Image not created from image source.");
return nil
};
return myImage;
}
二.通過原圖獲取縮略圖
func createThumbnailFromSource()-> CGImage?{
let myOptions = [kCGImageSourceShouldCache : kCFBooleanTrue,kCGImageSourceShouldAllowFloat : kCFBooleanTrue] as CFDictionary;
//這里我放了一張png圖片在工程中
guard let imgPath = Bundle.main.path(forResource: "IMG_0868", ofType: ".PNG")else{
return nil
}
guard let myImageSource = CGImageSourceCreateWithURL(URL(fileURLWithPath: imgPath) as CFURL, myOptions) else {
print(stderr, "Image source is NULL.");
return nil
}
let thumbnailOptions = [kCGImageSourceCreateThumbnailWithTransform : kCFBooleanTrue,kCGImageSourceCreateThumbnailFromImageIfAbsent : kCFBooleanTrue, kCGImageSourceThumbnailMaxPixelSize : 200] as CFDictionary;
// 生成縮略圖
guard let thumbnailImage = CGImageSourceCreateThumbnailAtIndex(myImageSource,0,thumbnailOptions)else {
print(stderr, "Image not created from image source.");
return nil
};
return thumbnailImage;
}
三.獲取圖片的相關信息
圖片視頻等文件其實都是一個壓縮包，里面包含很多信息，通過指定的格式解壓才有了我們看到的效果。圖片中就包含定位、拍攝設備、拍攝日期以及大小等等。通過CGImageSourceCopyPropertiesAtIndex就可以拿到這些信息，具體需要用到什么信息再自行加工。CGImageProperties詳細對照表
func getPropertiesFromImgSource() -> [String:Any]? {
// Create the dictionary
let myOptions : CFDictionary = [kCGImageSourceShouldCache : kCFBooleanTrue,kCGImageSourceShouldAllowFloat : kCFBooleanTrue] as CFDictionary;
// Create an image source from the URL.
guard let imgPath = Bundle.main.path(forResource: "IMG_0851", ofType: ".HEIC")else{
return nil
}
guard let myImageSource = CGImageSourceCreateWithURL(URL(fileURLWithPath: imgPath) as CFURL, myOptions) else {
print(stderr, "Image source is NULL.");
return nil
}
guard let props : NSDictionary = CGImageSourceCopyPropertiesAtIndex(myImageSource, 0, nil)else{
return nil
}
print(props)
//需要返回數據自行進行加工
return nil
}
打印內容
{
ColorModel = RGB;
DPIHeight = 72;
DPIWidth = 72;
Depth = 8;
Orientation = 1;
PixelHeight = 3024;
PixelWidth = 4032;
PrimaryImage = 1;
ProfileName = "Display P3";
"{Exif}" = {
...
};
"{GPS}" = {
...
};
"{MakerApple}" = {
...
};
"{TIFF}" = {
...
};
}
四.逐步加載圖片
在某些時候加載一張比較大的或者質量比較高的圖片，下載時間比較長。會影響用戶體驗，通過CGImageSourceUpdateData逐步更新圖片數據就會使體驗變得更好一些。
//用來接收請求返回的data
var imgData = Data()
//這里用本地網絡請求下載圖片，多張圖片加載時請使用多線程優(yōu)化，不做過多闡述
func createCreFromSource(){
let session = URLSession(configuration: URLSessionConfiguration.default, delegate: self, delegateQueue: nil)
let task = session.dataTask(with: URL(string: "http://localhost:8181/download?fileName=IMG_1438.JPG")!)
task.resume()
}
//通過URLSessionDataDelegate實現，不要用block，block會在拿到所有數據后觸發(fā)
func urlSession(_ session: URLSession, dataTask: URLSessionDataTask, didReceive data: Data) {
//拼接接收到的data數據
imgData.append(data)
let imageOptions = [kCGImageSourceShouldCache : kCFBooleanTrue,kCGImageSourceShouldAllowFloat : kCFBooleanTrue] as CFDictionary
let incrementSource = CGImageSourceCreateIncremental(nil)
CGImageSourceUpdateData(incrementSource, self.imgData as CFData, dataTask.countOfBytesExpectedToReceive == self.imgData.count)
let status = CGImageSourceGetStatus(incrementSource)
switch status {
case .statusComplete,.statusIncomplete:
if let cgImage = CGImageSourceCreateImageAtIndex(incrementSource, 0, imageOptions){
DispatchQueue.main.async {
//用到orientation因為測試圖片旋轉了90度，在查找原因
self.imgView.image = UIImage(cgImage: cgImage, scale: 1.0, orientation: UIImage.Orientation.right)
}
}
default:
break
}
}
