我正在尝试使用Accelerate vImageHistogramCalculation_ARGBFFFF
函数来计算图像的直方图,但我得到了vImage_Error
类型的kvImageNullPointerArgument
(错误代码是-21772
)。
这是完全相同的问题,但我在Swift工作:Compute the histogram of an image using vImageHistogramCalculation
// Get CGImage from UIImage
var image:UIImage = UIImage(named: "happiness1")!
var img:CGImageRef = image.CGImage
// Create vImage_Buffer with data from CGImageRef
var inProvider:CGDataProviderRef = CGImageGetDataProvider(img)
var inBitmapData:CFDataRef = CGDataProviderCopyData(inProvider)
// The next three lines set up the inBuffer object
var height:vImagePixelCount = CGImageGetHeight(img)
var width:vImagePixelCount = CGImageGetWidth(img)
var rowBytes:UInt = CGImageGetBytesPerRow(img)
var data:UnsafePointer<Void> = UnsafePointer<Void>(CFDataGetBytePtr(inBitmapData))
// Setup inBuffer
var inBuffer = vImage_Buffer(data: &data, height: height, width: width, rowBytes: rowBytes)
var histogram_entries:UInt32 = 4
var minVal:Pixel_F = 0
var maxVal:Pixel_F = 255
//let flags:vImage_Flags = kvImageNoFlags = 0
var histogram = UnsafeMutablePointer<UnsafeMutablePointer<vImagePixelCount>>()
var error:vImage_Error = vImageHistogramCalculation_ARGBFFFF(&inBuffer, histogram, histogram_entries, minVal, maxVal, 0)
println(error)
问题出在直方图变量中,我需要重新创建这样的东西:
// create an array of four histograms with eight entries each.
vImagePixelCount histogram[4][8] = {{0}};
// vImageHistogramCalculation requires an array of pointers to the histograms.
vImagePixelCount *histogramPointers[4] = { &histogram[0][0], &histogram[1][0], &histogram[2][0], &histogram[3][0] };
vImage_Error error = vImageHistogramCalculation_ARGBFFFF(&inBuffer, histogramPointers, 8, 0, 255, kvImageNoFlags);
// You can now access bin j of the histogram for channel i as histogram[i][j].
// The storage for the histogram will be cleaned up when execution leaves the
// current lexical block.
建议?
我已经实现了vImageHistogramCalculation_ARGB8888作为Swift中UIImage的扩展,具体如下:
func SIHistogramCalculation() -> (alpha: [UInt], red: [UInt], green: [UInt], blue: [UInt]) {
let imageRef = self.CGImage
let inProvider = CGImageGetDataProvider(imageRef)
let inBitmapData = CGDataProviderCopyData(inProvider)
var inBuffer = vImage_Buffer(data: UnsafeMutablePointer(CFDataGetBytePtr(inBitmapData)), height: UInt(CGImageGetHeight(imageRef)), width: UInt(CGImageGetWidth(imageRef)), rowBytes: CGImageGetBytesPerRow(imageRef))
var alpha = [UInt](count: 256, repeatedValue: 0)
var red = [UInt](count: 256, repeatedValue: 0)
var green = [UInt](count: 256, repeatedValue: 0)
var blue = [UInt](count: 256, repeatedValue: 0)
var alphaPtr = UnsafeMutablePointer<vImagePixelCount>(alpha)
var redPtr = UnsafeMutablePointer<vImagePixelCount>(red)
var greenPtr = UnsafeMutablePointer<vImagePixelCount>(green)
var bluePtr = UnsafeMutablePointer<vImagePixelCount> (blue)
var rgba = [redPtr, greenPtr, bluePtr, alphaPtr]
var histogram = UnsafeMutablePointer<UnsafeMutablePointer<vImagePixelCount>>(rgba)
var error = vImageHistogramCalculation_ARGB8888(&inBuffer, histogram, UInt32(kvImageNoFlags))
return (alpha, red, green, blue)
}