我正试图在Swift的CoreGraphics中的UIImageView中为一个动态几何软件应用程序绘制一个字符串。我使用上下文图形来绘制点和线，但当我尝试绘制文本字符串(例如，线段的长度(时，我要么没有得到文本(例如在这两个示例中(，要么除了文本字符串之外，我绘制的所有其他内容都被删除(对不起，我没有保存这些示例(。在后一种情况下，我可以在字符串上画其他东西，但这也没有真正的帮助，因为我只能画一个字符串(试图画第二个字符串会抹去第一个字符串(。
以下是两次尝试，均未绘制文本字符串：
UIGraphicsBeginImageContext(canvas.frame.size)
canvas.draw(CGRect(x: 0, y: 0, width: canvas.frame.width, height: canvas.frame.height))
let context = UIGraphicsGetCurrentContext()
let text="(value)"
let font=UIFont(name: "Helvetica", size: 12)!
let text_style=NSMutableParagraphStyle()
text_style.alignment=NSTextAlignment.center
let text_color=UIColor.black
let attributes=[NSAttributedString.Key.font:font, NSAttributedString.Key.paragraphStyle:text_style, NSAttributedString.Key.foregroundColor:text_color]
let text_x=coordinates.x
let text_y=coordinates.y
let text_rect=CGRect(x: text_x, y: text_y, width: 100, height: font.lineHeight)
text.draw(in: text_rect.integral, withAttributes: attributes)
UIGraphicsEndImageContext()
}```
```override func draw(_ canvas: UIImageView, _ isRed: Bool) {
UIGraphicsBeginImageContext(canvas.frame.size)
canvas.draw(CGRect(x: 0, y: 0, width: canvas.frame.width, height: canvas.frame.height))
let renderer = UIGraphicsImageRenderer(size: CGSize(width: 512, height: 512))
let img = renderer.image { ctx in
let paragraphStyle = NSMutableParagraphStyle()
paragraphStyle.alignment = .center
let attrs = [NSAttributedString.Key.font: UIFont(name: "HelveticaNeue-Thin", size: 12)!, NSAttributedString.Key.paragraphStyle: paragraphStyle]
let string = "(value)"
string.draw(with: CGRect(x: coordinates.x, y: coordinates.y, width: 100, height: 16), options: .usesLineFragmentOrigin, attributes: attrs, context: nil)
}
}```
I have also found a page that says something to the effect that it is impossible to draw text in a UIImageView. However, it is hard to believe that a graphics system as mature as core graphics wouldn't allow drawing text.
我正在MacOSCocoa中使用coreGraphic制作barChart。该程序为SwiftUI嵌入了一些有用的链接。你应该能够使我的代码适应你的程序。
// ViewController.swift
// Chart_test
//
// Created by slareau on 2022-10-10.
//
//https://stackoverflow.com/questions/38079917/drawing-in-cocoa-swift
//https://www.raywenderlich.com/1101-core-graphics-on-macos-tutorial
//https://stackoverflow.com/questions/10627557/mac-os-x-drawing-into-an-offscreen-nsgraphicscontext-using-cgcontextref-c-funct
//https://nshipster.com/cggeometry/
//https://www.hackingwithswift.com/example-code/core-graphics/how-to-draw-a-text-string-using-core-graphics
import Cocoa
import CoreGraphics
class ChartsVC: NSViewController {
override func viewDidLoad() {
super.viewDidLoad()
print("ChartsVC")
let dr = Drawing(frame: NSRect(x: 50, y: 50, width: 550, height: 500))
self.view.addSubview(dr)
}
}
class Drawing: NSView {
//var facts_list: [myfact] = [] //complete database
//var fact_total: [Double] = [0.0, 0.0, 0.0, 0.0, 0.0]
var fact_total: [Double] = [12454, 22365,18989, 14656, 16777]
//var comm_list: [myComm] = []
// var comm_total: [Double] = [0.0, 0.0, 0.0, 0.0, 0.0]
var comm_total: [Double] = [8976, 14989, 13989, 12065, 15040]
var Current_Year : Int = 0
var Current_Month : Int = 0
override func draw(_ dirtyRect: NSRect) {
super.draw(dirtyRect)
let todays_date = Date()
let dateFormatter = DateFormatter()
dateFormatter.dateFormat = "yyyy"
Current_Year = Int(dateFormatter.string(from: todays_date))!
// print ("VC60:", dateFormatter.string(from: todays_date), Current_Year!) OK
dateFormatter.dateFormat = "MM"
Current_Month = Int(dateFormatter.string(from: todays_date))!
// Load_CommDB()
// Load_FactDB()
var j = 0
while j < 5 { // last 5 years
print ( "VCH165: ", Current_Year - j, fact_total[j], comm_total[j] )
j += 1
}
// frame background
myRect(x: 0, y: 0, wd: 500, ht: 400, color: NSColor.lightGray)
for i in 0...4 {
let factT = String(fact_total[4 - i])
let commT = String(comm_total[4 - i])
let diffT = String(fact_total[4 - i] - comm_total[4 - i])
myRect(x: Double(50 + 80 * i) , y: 80, wd: 50, ht: Double(fact_total[4 - i]/100), color: NSColor.blue)
myRect(x: Double(60 + 80 * i) , y: 80, wd: 50, ht: Double(comm_total[4 - i]/100), color: NSColor.orange)
myRect(x: Double(70 + 80 * i) , y: 80, wd: 50, ht: Double((fact_total[4 - i] - comm_total[4 - i])/100), color: NSColor.green)
mytext(txt: factT.toCurrencyFormat(), x: Double(45 + 80 * i), y: 60)
mytext(txt: commT.toCurrencyFormat(), x: Double(45 + 80 * i), y: 40)
mytext(txt: diffT.toCurrencyFormat(), x: Double(45 + 80 * i), y: 20)
mytext(txt: String(Current_Year - (4 - i)), x: Double(45 + 80 * i), y: 3)
}
let context = NSGraphicsContext.current!.cgContext;
context.beginPath()
context.move(to: CGPoint(x: 10.0, y: 78.0))
context.addLine(to: CGPoint(x: 420.0, y: 78.0))
//context.setStrokeColor(red: 1, green: 0, blue: 0, alpha: 1)
context.setStrokeColor(NSColor.black.cgColor)
context.setLineWidth(2.0)
context.strokePath()
}
func myRect( x: Double, y: Double, wd: Double, ht :Double, color: NSColor) {
let context = NSGraphicsContext.current!.cgContext;
let rectangle = CGRect(x: x, y: y, width: wd, height: ht) // NSRect or CGRect work
//context.setFillColor(NSColor.yellow.cgColor)
context.setFillColor(color.cgColor)
context.setStrokeColor(NSColor.black.cgColor)
context.setLineWidth(2)
context.addRect(rectangle)
context.drawPath(using: .fillStroke)
}
func mytext ( txt: String, x: Double, y: Double) {
// let myfont = CTFontCreateWithName("Papyrus" as CFString, 12, nil)
let myfont = CTFontCreateWithName("Arial" as CFString, 12, nil)
let attributedString = NSAttributedString(string: txt, attributes: [NSAttributedString.Key.font: myfont])
// let attributedString = NSAttributedString(string: "allo le monde")
let line = CTLineCreateWithAttributedString(attributedString)
// Draw text
if let context = NSGraphicsContext.current?.cgContext {
context.textPosition = .init(x: x , y: y)
CTLineDraw(line, context)
}
//https://blog.krzyzanowskim.com/2020/07/09/coretext-academy-part-1/
//https://blog.krzyzanowskim.com/2020/07/10/coretext-swift-academy-part-2/
//https://blog.krzyzanowskim.com/2020/07/13/coretext-swift-academy-part-3/
}
}