70 lines
2.5 KiB
Swift
70 lines
2.5 KiB
Swift
//
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// WeChatThumbImageProcessor.swift
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// suixinkan
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//
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import UIKit
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/// 微信分享缩略图处理器，将图片压缩到微信 32KB 限制内。
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enum WeChatThumbImageProcessor {
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/// 微信缩略图最大字节数。
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static let maxThumbBytes = 32 * 1024
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/// 微信小程序预览图最大字节数。
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static let maxMiniProgramHDImageBytes = 128 * 1024
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/// 将图片压缩为符合微信要求的缩略图数据。
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static func makeThumbData(from image: UIImage, maxBytes: Int = maxThumbBytes) -> Data? {
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guard maxBytes > 0 else { return nil }
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let resized = resize(image, maxPixel: 120)
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var quality: CGFloat = 0.82
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var data = resized.jpegData(compressionQuality: quality)
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while let current = data, current.count > maxBytes, quality > 0.12 {
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quality -= 0.1
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data = resized.jpegData(compressionQuality: quality)
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}
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guard let result = data, result.count <= maxBytes else { return nil }
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return result
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}
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/// 将图片压缩为符合微信小程序分享要求的高清预览图数据。
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static func makeMiniProgramHDImageData(
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from image: UIImage,
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maxBytes: Int = maxMiniProgramHDImageBytes
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) -> Data? {
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guard maxBytes > 0 else { return nil }
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let resized = resize(image, maxPixel: 500)
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var quality: CGFloat = 0.86
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var data = resized.jpegData(compressionQuality: quality)
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while let current = data, current.count > maxBytes, quality > 0.12 {
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quality -= 0.08
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data = resized.jpegData(compressionQuality: quality)
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}
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guard let result = data, result.count <= maxBytes else { return nil }
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return result
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}
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/// 等比缩放图片，使最长边不超过指定像素。
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static func resize(_ image: UIImage, maxPixel: CGFloat) -> UIImage {
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let sourceSize = image.size
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guard sourceSize.width > 0, sourceSize.height > 0 else { return image }
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let maxSide = max(sourceSize.width, sourceSize.height)
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guard maxSide > maxPixel else { return image }
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let scale = maxPixel / maxSide
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let targetSize = CGSize(width: sourceSize.width * scale, height: sourceSize.height * scale)
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let format = UIGraphicsImageRendererFormat.default()
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format.scale = 1
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let renderer = UIGraphicsImageRenderer(size: targetSize, format: format)
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return renderer.image { _ in
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image.draw(in: CGRect(origin: .zero, size: targetSize))
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}
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}
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}
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