说我有一个从CGImage
加载的URL
,我想通过CGImageSourceCopyPropertiesAtIndex
提取其属性:
// Playground
import SwiftUI
func printPropertiesOf(_ image: CGImage) {
guard let dataProvider = image.dataProvider else {
print("Couldn't get the data provider.")
return
}
guard let data = dataProvider.data else {
print("Couldn't get the data.")
return
}
guard let source = CGImageSourceCreateWithData(data, nil) else {
print("Couldn't get the source.")
return
}
guard let properties = CGImageSourceCopyPropertiesAtIndex(source, 0, nil) else {
print("Couldn't get the properties.")
return
}
print(properties)
}
let url = Bundle.main.url(forResource: "Landscape/Landscape_0", withExtension: "jpg")!
let source = CGImageSourceCreateWithURL(url as CFURL, nil)!
let cgImage = CGImageSourceCreateImageAtIndex(source, 0, nil)!
printPropertiesOf(cgImage)
输出:
无法获取属性。
但是如果我使用图像所在的URL
,而不是CGImage
:
// Playground
import SwiftUI
func printPropertiesOfImageIn(_ url: URL) {
guard let data = try? Data(contentsOf: url) else {
print("Couldn't get the data.")
return
}
guard let source = CGImageSourceCreateWithData(data as CFData, nil) else {
print("Couldn't get the source.")
return
}
guard let properties = CGImageSourceCopyPropertiesAtIndex(source, 0, nil) else {
print("Couldn't get the properties.")
return
}
print(properties)
}
let url = Bundle.main.url(forResource: "Landscape/Landscape_0", withExtension: "jpg")!
let source = CGImageSourceCreateWithURL(url as CFURL, nil)!
let cgImage = CGImageSourceCreateImageAtIndex(source, 0, nil)!
printPropertiesOfImageIn(url)
输出:
{
ColorModel = RGB;
DPIHeight = 72;
DPIWidth = 72;
Depth = 8;
PixelHeight = 1200;
PixelWidth = 1800;
"{JFIF}" = {
DensityUnit = 1;
JFIFVersion = (
1,
0,
1
);
XDensity = 72;
YDensity = 72;
};
"{TIFF}" = {
Orientation = 0;
ResolutionUnit = 2;
XResolution = 72;
YResolution = 72;
};
}
是否有一种方法可以从
CGImage
本身检索元数据,不必依赖其源URL?如果没有,是否有办法找出给定的来源
URL
CGImage
?
((注:以上示例can be found here中使用的图像。)
CGImage
应该完全是原始位图数据。最少一组未压缩的数据,即使在视觉上也可以呈现图像。从docs“位图图像或图像蒙版”。