Question

我试图在函数CGImageSourceCreateThumbnailAtIndex的帮助下从现有CGImage生成缩略图。

在我发现的所有示例中，所提供的图像源都是在图像网址的帮助下创建的。

由于我没有任何网址 - 只有图片数据 - 我试过这样：

func createThumbnailForImage(image: CGImage, size: Int) -> CGImage?
{
    var provider = CGImageGetDataProvider(image)

    if let imageSource = CGImageSourceCreateWithDataProvider(provider, nil)
    {
        let swiftDict = [
            kCGImageSourceThumbnailMaxPixelSize as String : size,
            kCGImageSourceCreateThumbnailFromImageIfAbsent as String : true
        ]

        let nsDict = swiftDict as NSDictionary
        let cfDict = nsDict as CFDictionary

        return CGImageSourceCreateThumbnailAtIndex(imageSource, 0, cfDict)
    }

   return nil
}

我得到的结果总是零。

我的猜测是图像来源出了问题，但无法确定问题。

Answer 1

Swift 3有实现缩略图生成

import Foundation
import UIKit
import ImageIO

class PhotoUtils: NSObject {

static func thumbnail(url:CFURL) -> UIImage {
    let src = CGImageSourceCreateWithURL(url, nil)
    return thumbnailImage(src: src!)
}

static func thumbnail(data imageData:CFData) -> UIImage {
    let src = CGImageSourceCreateWithData(imageData, nil)
    return thumbnailImage(src: src!)
}

static private func thumbnailImage(src: CGImageSource) -> UIImage {
    let scale = UIScreen.main.scale
    let w = (UIScreen.main.bounds.width / 3) * scale
    let d : [NSObject:AnyObject] = [
        kCGImageSourceShouldAllowFloat : true as AnyObject,
        kCGImageSourceCreateThumbnailWithTransform : true as AnyObject,
        kCGImageSourceCreateThumbnailFromImageAlways : true as AnyObject,
        kCGImageSourceThumbnailMaxPixelSize : w as AnyObject
    ]
    let imref = CGImageSourceCreateThumbnailAtIndex(src, 0, d as CFDictionary)
    return UIImage(cgImage: imref!, scale: scale, orientation: .up)
}

}

使用ImageIO从现有CGImage生成图像缩略图？

1 个答案: