[英]I am getting unsupported parameter combination CGBitmap error with swift
我正在嘗試快速創建一個 CGContext 。 它編譯但在運行時拋出錯誤。
let colorSpace:CGColorSpace = CGColorSpaceCreateDeviceRGB()
let context:CGContext = CGBitmapContextCreate(nil, 20, 20, 8, 0, colorSpace, CGBitmapInfo.AlphaInfoMask)
CGColorSpaceRelease(colorSpace);
....
錯誤是:
Error: CGBitmapContextCreate: unsupported parameter combination: 8 integer bits/component; 32 bits/pixel; 3-component color space; unrecognized; 96 bytes/row.
fatal error: Can't unwrap Optional.None
以防萬一有人遇到同樣的問題。 下面的片段終於起作用了。
let colorSpace:CGColorSpace = CGColorSpaceCreateDeviceRGB()
let bitmapInfo = CGBitmapInfo(CGImageAlphaInfo.PremultipliedLast.rawValue)
let context = CGBitmapContextCreate(nil, UInt(rect.size.width), UInt(rect.size.height), 8, 0, colorSpace, bitmapInfo)
它迅速生成 32 位 RGBA 上下文
為 Swift 3 更新:
let colorSpace = CGColorSpaceCreateDeviceRGB()
let bitmapInfo = CGBitmapInfo(rawValue: CGImageAlphaInfo.premultipliedLast.rawValue)
guard let context = CGContext.init(data: nil, width: Int(size.width), height: Int(size.height), bitsPerComponent: Int(bitsPerComponent), bytesPerRow: Int(bytesPerRow), space: colorSpace, bitmapInfo: UInt32(bitmapInfo.rawValue)) else {
// cannot create context - handle error
}
在 Swift 2.1 中,可以正確訪問字段,甚至可以將它們組合在一起:
let bitmapInfo = CGBitmapInfo(rawValue: CGImageAlphaInfo.PremultipliedFirst.rawValue | CGBitmapInfo.ByteOrder32Little.rawValue)
let context = CGBitmapContextCreate(baseAddress, width, height, 8,
bytesPerRow, colorSpace, bitmapInfo.rawValue);
大量的 'rawValue' 正在進行 :)
你甚至不需要把bitmapInfo分開,就可以做一個單行:
let context = CGBitmapContextCreate(baseAddress, width, height, 8,
bytesPerRow, colorSpace, CGImageAlphaInfo.PremultipliedFirst.rawValue | CGBitmapInfo.ByteOrder32Little.rawValue
為Swift 5更新:
let colorSpace:CGColorSpace = CGColorSpaceCreateDeviceRGB()
let bitmapInfo = CGBitmapInfo(rawValue: CGImageAlphaInfo.premultipliedLast.rawValue)
let context = CGContext(data: nil, width: UInt(rect.size.width), height: UInt(rect.size.height), bitsPerComponent: 8, bytesPerRow: 0, space: colorSpace, bitmapInfo: bitmapInfo.rawValue)
其中 rect 具有高度和寬度
我在使用UInt
Swift 1.2 中遇到了一些問題,現在我使用的是Int
並且它正在工作。 此示例顯示如何將圖像轉換為灰度圖像。
let imageRect = self.myImage.frame
let colorSpace = CGColorSpaceCreateDeviceGray()
let width = imageRect.width
let height = imageRect.height
let bitmapInfo = CGBitmapInfo(CGImageAlphaInfo.None.rawValue)
let context = CGBitmapContextCreate(nil, Int(width), Int(height), 8, 0, colorSpace, bitmapInfo)
與支持Swift 3和Swift 4 的Xcode 8.3和Xcode 9兼容的建議方式
let colorSpace = CGColorSpaceCreateDeviceRGB()
guard let bitmapContext = CGContext(data: nil,
width: Int(size.width),
height: Int(size.height),
bitsPerComponent: Int(bitsPerComponent),
bytesPerRow: Int(bytesPerRow),
space: colorSpace,
bitmapInfo: CGImageAlphaInfo.premultipliedLast.rawValue) else {
return nil
}
在 Swift 2.2 中:
let bitmapInfo = CGBitmapInfo(rawValue: CGImageAlphaInfo.PremultipliedLast.rawValue).rawValue
let colorSpace = CGColorSpaceCreateDeviceRGB()
let context = CGBitmapContextCreate(nil, Int(width), Int(height), 8, 0, colorSpace, bitmapInfo)
CGBitmapInfo.AlphaInfoMask 不是有效的位圖信息。
嘗試設置 CGBitmapInfo.AlphaLast 或 CGBitmapInfo.AlphaFirst。
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