我有一个 UIImage,它是一个轮廓,一个是填充的,两者都是从 OpenCV 创建的,一个来自抓取,另一个来自结构化元素。
我的两张图片是这样的:
我试图更改轮廓图像中的所有白色像素,因为我想将两个图像合并在一起,所以我最终得到一个红色轮廓和中间的白色填充区域。我正在使用它来将两者合并在一起,我知道它不是红色,而是一种粉红色,灰色而不是白色,因为我只是将它们与 alpha 混合在一起。
// Start an image context
UIGraphicsBeginImageContext(grabcutResult.size)
// Create rect for this draw session
let rect = CGRect(x: 0.0, y: 0.0, width: grabcutResult.size.width, height: grabcutResult.size.height)
grabcutResult.draw(in: rect)
redGrabcutOutline.draw(in: rect, blendMode: .normal, alpha: 0.5)
let finalImage = UIGraphicsGetImageFromCurrentImageContext()
想法是它应该看起来像这样。
我希望能够快速完成此操作,但我找到的唯一解决方案是 ImageView(它只影响内容的呈现方式而不影响底层 UIImage),或者它们涉及逐个像素地遍历整个图像。
我正在尝试找到一种解决方案,它将轮廓中的所有白色像素都屏蔽为红色,而不必逐个像素地遍历整个图像,因为它太慢了。
理想情况下,如果我能让 openCV 只返回红色轮廓而不是白色轮廓,那会很好,但我认为不可能改变它(也许我错了)。
顺便说一句,使用 swift ......但感谢任何帮助,在此先感谢。
最佳答案
这可能对您有用——仅使用 Swift 代码...
extension UIImage {
func maskWithColor(color: UIColor) -> UIImage? {
let maskingColors: [CGFloat] = [1, 255, 1, 255, 1, 255]
let bounds = CGRect(origin: .zero, size: size)
let maskImage = cgImage!
var returnImage: UIImage?
// make sure image has no alpha channel
let rFormat = UIGraphicsImageRendererFormat()
rFormat.opaque = true
let renderer = UIGraphicsImageRenderer(size: size, format: rFormat)
let noAlphaImage = renderer.image {
(context) in
self.draw(at: .zero)
}
let noAlphaCGRef = noAlphaImage.cgImage
if let imgRefCopy = noAlphaCGRef?.copy(maskingColorComponents: maskingColors) {
let rFormat = UIGraphicsImageRendererFormat()
rFormat.opaque = false
let renderer = UIGraphicsImageRenderer(size: size, format: rFormat)
returnImage = renderer.image {
(context) in
context.cgContext.clip(to: bounds, mask: maskImage)
context.cgContext.setFillColor(color.cgColor)
context.cgContext.fill(bounds)
context.cgContext.draw(imgRefCopy, in: bounds)
}
}
return returnImage
}
}
此扩展返回一个 UIImage
,其中白色替换为传递的 UIColor
,黑色“背景”变为透明。
以这种方式使用它:
// change filled white star to gray with transparent background
let modFilledImage = filledImage.maskWithColor(color: UIColor(red: 200, green: 200, blue: 200))
// change outlined white star to red with transparent background
let modOutlineImage = outlineImage.maskWithColor(color: UIColor.red)
// combine the images on a black background
这是一个完整的示例,使用您的两个原始图像(大部分代码设置 ImageView 以显示结果):
extension UIImage {
func maskWithColor(color: UIColor) -> UIImage? {
let maskingColors: [CGFloat] = [1, 255, 1, 255, 1, 255]
let bounds = CGRect(origin: .zero, size: size)
let maskImage = cgImage!
var returnImage: UIImage?
// make sure image has no alpha channel
let rFormat = UIGraphicsImageRendererFormat()
rFormat.opaque = true
let renderer = UIGraphicsImageRenderer(size: size, format: rFormat)
let noAlphaImage = renderer.image {
(context) in
self.draw(at: .zero)
}
let noAlphaCGRef = noAlphaImage.cgImage
if let imgRefCopy = noAlphaCGRef?.copy(maskingColorComponents: maskingColors) {
let rFormat = UIGraphicsImageRendererFormat()
rFormat.opaque = false
let renderer = UIGraphicsImageRenderer(size: size, format: rFormat)
returnImage = renderer.image {
(context) in
context.cgContext.clip(to: bounds, mask: maskImage)
context.cgContext.setFillColor(color.cgColor)
context.cgContext.fill(bounds)
context.cgContext.draw(imgRefCopy, in: bounds)
}
}
return returnImage
}
}
class MaskWorkViewController: UIViewController {
let origFilledImgView: UIImageView = {
let v = UIImageView()
v.translatesAutoresizingMaskIntoConstraints = false
v.contentMode = .center
return v
}()
let origOutlineImgView: UIImageView = {
let v = UIImageView()
v.translatesAutoresizingMaskIntoConstraints = false
v.contentMode = .center
return v
}()
let modifiedFilledImgView: UIImageView = {
let v = UIImageView()
v.translatesAutoresizingMaskIntoConstraints = false
v.contentMode = .center
return v
}()
let modifiedOutlineImgView: UIImageView = {
let v = UIImageView()
v.translatesAutoresizingMaskIntoConstraints = false
v.contentMode = .center
return v
}()
let combinedImgView: UIImageView = {
let v = UIImageView()
v.translatesAutoresizingMaskIntoConstraints = false
v.contentMode = .center
return v
}()
let origStack: UIStackView = {
let v = UIStackView()
v.translatesAutoresizingMaskIntoConstraints = false
v.axis = .horizontal
v.spacing = 20
return v
}()
let modifiedStack: UIStackView = {
let v = UIStackView()
v.translatesAutoresizingMaskIntoConstraints = false
v.axis = .horizontal
v.spacing = 20
return v
}()
let mainStack: UIStackView = {
let v = UIStackView()
v.translatesAutoresizingMaskIntoConstraints = false
v.axis = .vertical
v.alignment = .center
v.spacing = 10
return v
}()
override func viewDidLoad() {
super.viewDidLoad()
guard let filledImage = UIImage(named: "StarFill"),
let outlineImage = UIImage(named: "StarEdge") else {
return
}
var modifiedFilledImage: UIImage = UIImage()
var modifiedOutlineImage: UIImage = UIImage()
var combinedImage: UIImage = UIImage()
// for both original images, replace white with color
// and make black transparent
if let modFilledImage = filledImage.maskWithColor(color: UIColor(red: 200, green: 200, blue: 200)),
let modOutlineImage = outlineImage.maskWithColor(color: UIColor.red) {
modifiedFilledImage = modFilledImage
modifiedOutlineImage = modOutlineImage
let rFormat = UIGraphicsImageRendererFormat()
rFormat.opaque = true
let renderer = UIGraphicsImageRenderer(size: modifiedFilledImage.size, format: rFormat)
// combine modified images on black background
combinedImage = renderer.image {
(context) in
context.cgContext.setFillColor(UIColor.black.cgColor)
context.cgContext.fill(CGRect(origin: .zero, size: modifiedFilledImage.size))
modifiedFilledImage.draw(at: .zero)
modifiedOutlineImage.draw(at: .zero)
}
}
// setup image views and set .image properties
setupUI(filledImage.size)
origFilledImgView.image = filledImage
origOutlineImgView.image = outlineImage
modifiedFilledImgView.image = modifiedFilledImage
modifiedOutlineImgView.image = modifiedOutlineImage
combinedImgView.image = combinedImage
}
func setupUI(_ imageSize: CGSize) -> Void {
origStack.addArrangedSubview(origFilledImgView)
origStack.addArrangedSubview(origOutlineImgView)
modifiedStack.addArrangedSubview(modifiedFilledImgView)
modifiedStack.addArrangedSubview(modifiedOutlineImgView)
var lbl = UILabel()
lbl.textAlignment = .center
lbl.text = "Original Images"
mainStack.addArrangedSubview(lbl)
mainStack.addArrangedSubview(origStack)
lbl = UILabel()
lbl.textAlignment = .center
lbl.numberOfLines = 0
lbl.text = "Modified Images\n(UIImageViews have Green Background)"
mainStack.addArrangedSubview(lbl)
mainStack.addArrangedSubview(modifiedStack)
lbl = UILabel()
lbl.textAlignment = .center
lbl.text = "Combined on Black Background"
mainStack.addArrangedSubview(lbl)
mainStack.addArrangedSubview(combinedImgView)
view.addSubview(mainStack)
NSLayoutConstraint.activate([
mainStack.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor, constant: 20.0),
mainStack.centerXAnchor.constraint(equalTo: view.centerXAnchor, constant: 0.0),
])
[origFilledImgView, origOutlineImgView, modifiedFilledImgView, modifiedOutlineImgView, combinedImgView].forEach {
$0.backgroundColor = .green
NSLayoutConstraint.activate([
$0.widthAnchor.constraint(equalToConstant: imageSize.width),
$0.heightAnchor.constraint(equalToConstant: imageSize.height),
])
}
}
}
结果,显示原始、修改和最终组合图像... ImageView 具有绿色背景以显示透明区域:
关于ios - 更改 UIImage 中的白色像素,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/58307979/