我正在尝试访问内在矩阵answer https://stackoverflow.com/a/48159895/9296667.
通过运行下面的命令，我能够得到一个 48 字节的任意对象 https://developer.apple.com/documentation/swift/anyobject，我进一步将其转换为CFData https://developer.apple.com/documentation/corefoundation/cfdata-rv9.
let camData = CMGetAttachment(sampleBuffer, kCMSampleBufferAttachmentKey_CameraIntrinsicMatrix, nil)
但是，我检查了sampleBuffer的输出CMSampleBuffer.h:
/*! @constant kCMSampleBufferAttachmentKey_CameraIntrinsicMatrix
@abstract Indicates the 3x3 camera intrinsic matrix applied to the current sample buffer.
@discussion Camera intrinsic matrix is a CFData containing a matrix_float3x3, which is column-major.
....
*/
CM_EXPORT const CFStringRef kCMSampleBufferAttachmentKey_CameraIntrinsicMatrix // CFData (matrix_float3x3) __OSX_AVAILABLE_STARTING(__MAC_NA,__IPHONE_11_0);
我应该如何访问其中的值matrix_float3x3来自CFData?
这应该有效：
- 使用桥接
CFData to NSData to Data, and
- the
withUnsafeBytes方法来获取所需的指针
输入数据字节，
-
.pointee取消引用指针。
Example:
if let camData = CMGetAttachment(sampleBuffer, kCMSampleBufferAttachmentKey_CameraIntrinsicMatrix, nil) as? Data {
let matrix: matrix_float3x3 = camData.withUnsafeBytes { $0.pointee }
// ...
}
指针类型（$0在闭包内）是从上下文推断出来的
作为UnsafePointer<matrix_float3x3>.
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