[英]Get average color of UIImage in Swift
我最近試圖將代碼從這里轉換為Swift。 但是,無論圖像如何,我都會保持白色。 這是我的代碼:
// Playground - noun: a place where people can play
import UIKit
extension UIImage {
func averageColor() -> UIColor {
var colorSpace = CGColorSpaceCreateDeviceRGB()
var rgba: [CGFloat] = [0,0,0,0]
var context = CGBitmapContextCreate(&rgba, 1, 1, 8, 4, colorSpace, CGBitmapInfo.fromRaw(CGImageAlphaInfo.PremultipliedLast.toRaw())!)
rgba
CGContextDrawImage(context, CGRectMake(0, 0, 1, 1), self.CGImage)
if rgba[3] > 0 {
var alpha = rgba[3] / 255
var multiplier = alpha / 255
return UIColor(red: rgba[0] * multiplier, green: rgba[1] * multiplier, blue: rgba[2] * multiplier, alpha: alpha)
} else {
return UIColor(red: rgba[0] / 255, green: rgba[1] / 255, blue: rgba[2] / 255, alpha: rgba[3] / 255)
}
}
}
var img = UIImage(data: NSData(contentsOfURL: NSURL(string: "http://upload.wikimedia.org/wikipedia/commons/c/c3/Aurora_as_seen_by_IMAGE.PNG")))
img.averageColor()
提前致謝。
iOS 9中的CoreImage:使用CIAreaAverage過濾器並傳遞整個圖像的范圍以進行平均。
此外,它要快得多,因為它要么在GPU上運行,要么作為高度優化的CPU CIKernel運行。
import UIKit
extension UIImage {
func areaAverage() -> UIColor {
var bitmap = [UInt8](count: 4, repeatedValue: 0)
if #available(iOS 9.0, *) {
// Get average color.
let context = CIContext()
let inputImage = CIImage ?? CoreImage.CIImage(CGImage: CGImage!)
let extent = inputImage.extent
let inputExtent = CIVector(x: extent.origin.x, y: extent.origin.y, z: extent.size.width, w: extent.size.height)
let filter = CIFilter(name: "CIAreaAverage", withInputParameters: [kCIInputImageKey: inputImage, kCIInputExtentKey: inputExtent])!
let outputImage = filter.outputImage!
let outputExtent = outputImage.extent
assert(outputExtent.size.width == 1 && outputExtent.size.height == 1)
// Render to bitmap.
context.render(outputImage, toBitmap: &bitmap, rowBytes: 4, bounds: CGRect(x: 0, y: 0, width: 1, height: 1), format: kCIFormatRGBA8, colorSpace: CGColorSpaceCreateDeviceRGB())
} else {
// Create 1x1 context that interpolates pixels when drawing to it.
let context = CGBitmapContextCreate(&bitmap, 1, 1, 8, 4, CGColorSpaceCreateDeviceRGB(), CGBitmapInfo.ByteOrderDefault.rawValue | CGImageAlphaInfo.PremultipliedLast.rawValue)!
let inputImage = CGImage ?? CIContext().createCGImage(CIImage!, fromRect: CIImage!.extent)
// Render to bitmap.
CGContextDrawImage(context, CGRect(x: 0, y: 0, width: 1, height: 1), inputImage)
}
// Compute result.
let result = UIColor(red: CGFloat(bitmap[0]) / 255.0, green: CGFloat(bitmap[1]) / 255.0, blue: CGFloat(bitmap[2]) / 255.0, alpha: CGFloat(bitmap[3]) / 255.0)
return result
}
}
斯威夫特3
func areaAverage() -> UIColor {
var bitmap = [UInt8](repeating: 0, count: 4)
if #available(iOS 9.0, *) {
// Get average color.
let context = CIContext()
let inputImage: CIImage = ciImage ?? CoreImage.CIImage(cgImage: cgImage!)
let extent = inputImage.extent
let inputExtent = CIVector(x: extent.origin.x, y: extent.origin.y, z: extent.size.width, w: extent.size.height)
let filter = CIFilter(name: "CIAreaAverage", withInputParameters: [kCIInputImageKey: inputImage, kCIInputExtentKey: inputExtent])!
let outputImage = filter.outputImage!
let outputExtent = outputImage.extent
assert(outputExtent.size.width == 1 && outputExtent.size.height == 1)
// Render to bitmap.
context.render(outputImage, toBitmap: &bitmap, rowBytes: 4, bounds: CGRect(x: 0, y: 0, width: 1, height: 1), format: kCIFormatRGBA8, colorSpace: CGColorSpaceCreateDeviceRGB())
} else {
// Create 1x1 context that interpolates pixels when drawing to it.
let context = CGContext(data: &bitmap, width: 1, height: 1, bitsPerComponent: 8, bytesPerRow: 4, space: CGColorSpaceCreateDeviceRGB(), bitmapInfo: CGImageAlphaInfo.premultipliedLast.rawValue)!
let inputImage = cgImage ?? CIContext().createCGImage(ciImage!, from: ciImage!.extent)
// Render to bitmap.
context.draw(inputImage!, in: CGRect(x: 0, y: 0, width: 1, height: 1))
}
// Compute result.
let result = UIColor(red: CGFloat(bitmap[0]) / 255.0, green: CGFloat(bitmap[1]) / 255.0, blue: CGFloat(bitmap[2]) / 255.0, alpha: CGFloat(bitmap[3]) / 255.0)
return result
}
這是一個解決方案:
func averageColor() -> UIColor {
let rgba = UnsafeMutablePointer<CUnsignedChar>.alloc(4)
let colorSpace: CGColorSpaceRef = CGColorSpaceCreateDeviceRGB()
let info = CGBitmapInfo(CGImageAlphaInfo.PremultipliedLast.rawValue)
let context: CGContextRef = CGBitmapContextCreate(rgba, 1, 1, 8, 4, colorSpace, info)
CGContextDrawImage(context, CGRectMake(0, 0, 1, 1), self.CGImage)
if rgba[3] > 0 {
let alpha: CGFloat = CGFloat(rgba[3]) / 255.0
let multiplier: CGFloat = alpha / 255.0
return UIColor(red: CGFloat(rgba[0]) * multiplier, green: CGFloat(rgba[1]) * multiplier, blue: CGFloat(rgba[2]) * multiplier, alpha: alpha)
} else {
return UIColor(red: CGFloat(rgba[0]) / 255.0, green: CGFloat(rgba[1]) / 255.0, blue: CGFloat(rgba[2]) / 255.0, alpha: CGFloat(rgba[3]) / 255.0)
}
}
斯威夫特3:
func areaAverage() -> UIColor {
var bitmap = [UInt8](repeating: 0, count: 4)
let context = CIContext(options: nil)
let cgImg = context.createCGImage(CoreImage.CIImage(cgImage: self.cgImage!), from: CoreImage.CIImage(cgImage: self.cgImage!).extent)
let inputImage = CIImage(cgImage: cgImg!)
let extent = inputImage.extent
let inputExtent = CIVector(x: extent.origin.x, y: extent.origin.y, z: extent.size.width, w: extent.size.height)
let filter = CIFilter(name: "CIAreaAverage", withInputParameters: [kCIInputImageKey: inputImage, kCIInputExtentKey: inputExtent])!
let outputImage = filter.outputImage!
let outputExtent = outputImage.extent
assert(outputExtent.size.width == 1 && outputExtent.size.height == 1)
// Render to bitmap.
context.render(outputImage, toBitmap: &bitmap, rowBytes: 4, bounds: CGRect(x: 0, y: 0, width: 1, height: 1), format: kCIFormatRGBA8, colorSpace: CGColorSpaceCreateDeviceRGB())
// Compute result.
let result = UIColor(red: CGFloat(bitmap[0]) / 255.0, green: CGFloat(bitmap[1]) / 255.0, blue: CGFloat(bitmap[2]) / 255.0, alpha: CGFloat(bitmap[3]) / 255.0)
return result
}
您是否正確設置了上下文? 如果我查看CGBitmapContext參考的文檔:
看起來你只為CGFloat數組中包含的圖像分配足夠的內存。 看起來你也告訴編譯器你的圖像只是一個像素一個像素。
當您在CGContextDrawImage中設置CGRect時,看起來該大小也被確認為一個像素一個像素。
如果Playground只是逐個像素地創建一個圖像,那么這就解釋了為什么你只看到一個白色的屏幕。
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