ios - 在 iOS Swift 3 中将 openGL ES 绘图保存为 PNG 图像文件

Question

我正在尝试使用 CGDataProvider 和 CGI​​mage 函数将使用 openGL ES 在 iOS 上生成的绘图保存到 PNG 文件。我在网上找到了一些 Objective-C 代码，我将其转换为 Swift 3。代码可以编译，但在运行时失败并抛出错误: fatal error :在这一行解包可选值时意外发现 nil:

let iref: CGImage = CGImage(pngDataProviderSource: provider!, decode: nil, shouldInterpolate: true, intent: CGColorRenderingIntent.defaultIntent)!

代码:

let x: Int = 0
let y: Int = 0
let dataLength: Int = Int(width) * Int(height) * 4
let pixels: UnsafeMutableRawPointer? = malloc(dataLength * MemoryLayout<GLubyte>.size)
glPixelStorei(GL_PACK_ALIGNMENT.ui, 4)
glReadPixels(GLint(x), GLint(y), GLsizei(width), GLsizei(height), GLenum(GL_RGBA), GL_UNSIGNED_BYTE.ui, pixels)
let pixelData: UnsafePointer = (UnsafeRawPointer(pixels)?.assumingMemoryBound(to: UInt8.self))!
let cfdata: CFData = CFDataCreate(kCFAllocatorDefault, pixelData, dataLength * MemoryLayout<GLubyte>.size)

let provider: CGDataProvider! = CGDataProvider(data: cfdata)

let iref: CGImage = CGImage(pngDataProviderSource: provider!, decode: nil, shouldInterpolate: true, intent: CGColorRenderingIntent.defaultIntent)!
UIGraphicsBeginImageContext(CGSize(width: CGFloat(width), height: CGFloat(height)))
let cgcontext: CGContext? = UIGraphicsGetCurrentContext()
cgcontext!.setBlendMode(CGBlendMode.copy)
cgcontext!.draw(iref, in: CGRect(x: CGFloat(0.0), y: CGFloat(0.0), width: CGFloat(width), height: CGFloat(height)))
let image: UIImage? = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()

我在网络上找不到 Swift 3 的任何帮助。您能否帮助修复此错误。

Answer 1

按照Matic Oblak的建议，当我替换上面代码中的这一行时，错误消失了并且代码正常工作

let iref: CGImage = CGImage(pngDataProviderSource: provider!, decode: nil, shouldInterpolate: true, intent: CGColorRenderingIntent.defaultIntent)!

有了这个

let iref: CGImage? = CGImage(width: Int(width), height: Int(height), bitsPerComponent: 8, bitsPerPixel: 32, bytesPerRow: Int(width)*4, space: colorspace!, bitmapInfo: CGBitmapInfo.byteOrder32Big, provider: provider, decode: nil, shouldInterpolate: true, intent: CGColorRenderingIntent.defaultIntent)

新的工作代码:

let x: Int = 0
let y: Int = 0
let dataLength: Int = Int(width) * Int(height) * 4
let pixels: UnsafeMutableRawPointer? = malloc(dataLength * MemoryLayout<GLubyte>.size)
glPixelStorei(GL_PACK_ALIGNMENT.ui, 4)
glReadPixels(GLint(x), GLint(y), GLsizei(width), GLsizei(height), GLenum(GL_RGBA), GL_UNSIGNED_BYTE.ui, pixels)
let pixelData: UnsafePointer = (UnsafeRawPointer(pixels)?.assumingMemoryBound(to: UInt8.self))!
let cfdata: CFData = CFDataCreate(kCFAllocatorDefault, pixelData, dataLength * MemoryLayout<GLubyte>.size)

let provider: CGDataProvider! = CGDataProvider(data: cfdata)

let iref: CGImage? = CGImage(width: Int(width), height: Int(height), bitsPerComponent: 8, bitsPerPixel: 32, bytesPerRow: Int(width)*4, space: colorspace!, bitmapInfo: CGBitmapInfo.byteOrder32Big, provider: provider, decode: nil, shouldInterpolate: true, intent: CGColorRenderingIntent.defaultIntent)
UIGraphicsBeginImageContext(CGSize(width: CGFloat(width), height: CGFloat(height)))
let cgcontext: CGContext? = UIGraphicsGetCurrentContext()
cgcontext!.setBlendMode(CGBlendMode.copy)
cgcontext!.draw(iref, in: CGRect(x: CGFloat(0.0), y: CGFloat(0.0), width: CGFloat(width), height: CGFloat(height)))
let image: UIImage? = UIGraphicsGetImageFromCurrentImageContext()
UIGraphicsEndImageContext()