是否可以使用本机 iOS API 加载 24 位 BMP？

Question

我正在为一个设备编写一个应用程序，该设备 API 为我们提供了一个 const char* 字节数组，对应于具有 24 位色深的 BMP 的像素数据，Core Graphics 不支持，所以我循环遍历字节，为 alpha 通道添加第四个字节，然后使用 CGImageAlphaInfo.noneSkipLast:

跳过它

let imageProperties = /* call to the device API that returns the image metadata */
let imageData = UnsafeMutablePointer<CChar>(mutating: /* call to the device API that returns the pointer */)

let imageWidth = Int(imageProperties.width)
let imageHeight = Int(imageProperties.height)
let bytesPerPixelWithoutAlpha = 3
let imageSize = imageWidth * imageHeight * bytesPerPixelWithoutAlpha
var imageDataWithAlpha = [CChar]()
for i in stride(from: 0, to: imageSize, by: bytesPerPixelWithoutAlpha) {
    imageDataWithAlpha.append(imageData![i])
    imageDataWithAlpha.append(imageData![i + 1])
    imageDataWithAlpha.append(imageData![i + 2])
    imageDataWithAlpha.append(127)
}
let bytesPerPixelWithAlpha = 4
let bytesPerRow = imageWidth * bytesPerPixelWithAlpha
let imageDataWithAlphaPointer = UnsafeMutablePointer<CChar>.allocate(capacity: imageDataWithAlpha.count)
imageDataWithAlphaPointer.initialize(from: &imageDataWithAlpha, count: imageDataWithAlpha.count)

let bmp = CGContext(
    data: imageDataWithAlphaPointer,
    width: imageWidth,
    height: imageHeight,
    bitsPerComponent: 8,
    bytesPerRow: bytesPerRow,
    space: CGColorSpaceCreateDeviceRGB(),
    bitmapInfo: CGImageAlphaInfo.noneSkipLast.rawValue
)!.makeImage()!

bmp 被传递给 CIContext().writeJPEGRepresentation 以将 JPEG 写入磁盘，它可以工作，但我的代码有味道，我敢打赌我可以使用其他一些 API我的循环

Answer 1

我认为您可以用适当的格式将数据包装成 CVPixelBuffer 并将其传递给 Core Image。类似的东西：

var pixelBuffer: CVPixelBuffer?
let result = CVPixelBufferCreateWithBytes(kCFAllocatorDefault,
                                          imageWidth,
                                          imageHeight,
                                          kCVPixelFormatType_24RGB,
                                          imageData,
                                          3 * imageWidth,
                                          nil,
                                          nil,
                                          nil,
                                          &pixelBuffer)
guard result == kCVReturnSuccess, let pixelBuffer = pixelBuffer else {
    fatalError()
}
let image = CIImage(cvPixelBuffer: pixelBuffer)
// ...

Core Image 应根据需要自动填充 alpha 通道。

是否可以使用本机 iOS API 加载 24 位 BMP？

Is it possible to load a 24-bits BMP with a native iOS API?

core-graphics

core-image

ios