added MTMathImage - draw latex image offscreen.

Sources/SwiftMath/MathRender/MTConfig.swift

@@ -18,6 +18,7 @@ public typealias MTBezierPath = UIBezierPath
 public typealias MTLabel = UILabel
 public typealias MTEdgeInsets = UIEdgeInsets
 public typealias MTRect = CGRect
+public typealias MTImage = UIImage
 
 let MTEdgeInsetsZero = UIEdgeInsets.zero
 func MTGraphicsGetCurrentContext() -> CGContext? { UIGraphicsGetCurrentContext() }
@@ -31,6 +32,7 @@ public typealias MTColor = NSColor
 public typealias MTBezierPath = NSBezierPath
 public typealias MTEdgeInsets = NSEdgeInsets
 public typealias MTRect = NSRect
+public typealias MTImage = NSImage
 
 let MTEdgeInsetsZero = NSEdgeInsets.init(top: 0, left: 0, bottom: 0, right: 0)
 func MTGraphicsGetCurrentContext() -> CGContext? { NSGraphicsContext.current?.cgContext }

Sources/SwiftMath/MathRender/MTFontManager.swift

@@ -11,17 +11,16 @@ import Foundation
 
 public class MTFontManager {
     
-    static public private(set) var manager:MTFontManager! = nil
+    static public private(set) var manager: MTFontManager = {
+        MTFontManager()
+    }()
     
     let kDefaultFontSize = CGFloat(20)
     
     static var fontManager : MTFontManager {
-        if manager == nil {
-            manager = MTFontManager()
-        }
-        return manager!
+        return manager
     }
-    
+
     public init() { }
     
     var nameToFontMap = [String: MTFont]()

Sources/SwiftMath/MathRender/MTMathImage.swift

@@ -0,0 +1,111 @@
+//
+//  File.swift
+//  
+//
+//  Created by Peter Tang on 12/9/2023.
+//
+
+import Foundation
+
+#if os(iOS)
+    import UIKit
+#endif
+
+#if os(macOS)
+    import AppKit
+#endif
+
+public class MTMathImage {
+    public var font: MTFont? = nil
+    public let fontSize: CGFloat
+    public let textColor: MTColor
+
+    public let labelMode: MTMathUILabelMode
+    public let textAlignment: MTTextAlignment
+
+    public var contentInsets: MTEdgeInsets = MTEdgeInsetsZero
+    
+    public let latex: String
+    private(set) var intrinsicContentSize = CGSize.zero
+
+    public init(latex: String, fontSize: CGFloat, textColor: MTColor, labelMode: MTMathUILabelMode = .display, textAlignment: MTTextAlignment = .center) {
+        self.latex = latex
+        self.fontSize = fontSize
+        self.textColor = textColor
+        self.labelMode = labelMode
+        self.textAlignment = textAlignment
+    }
+}
+extension MTMathImage {
+    public var currentStyle: MTLineStyle {
+        switch labelMode {
+            case .display: return .display
+            case .text: return .text
+        }
+    }
+    private func intrinsicContentSize(_ displayList: MTMathListDisplay) -> CGSize {
+        CGSize(width: displayList.width + contentInsets.left + contentInsets.right,
+               height: displayList.ascent + displayList.descent + contentInsets.top + contentInsets.bottom)
+    }
+    public func asImage() -> (NSError?, MTImage?) {
+        func layoutImage(size: CGSize, displayList: MTMathListDisplay) {
+            var textX = CGFloat(0)
+            switch self.textAlignment {
+                case .left:   textX = contentInsets.left
+                case .center: textX = (size.width - contentInsets.left - contentInsets.right - displayList.width) / 2 + contentInsets.left
+                case .right:  textX = size.width - displayList.width - contentInsets.right
+            }
+            let availableHeight = size.height - contentInsets.bottom - contentInsets.top
+            
+            // center things vertically
+            var height = displayList.ascent + displayList.descent
+            if height < fontSize/2 {
+                height = fontSize/2  // set height to half the font size
+            }
+            let textY = (availableHeight - height) / 2 + displayList.descent + contentInsets.bottom
+            displayList.position = CGPoint(x: textX, y: textY)
+        }
+        if font == nil {
+            self.font = MTFontManager.fontManager.defaultFont
+        }
+        var error: NSError?
+        guard let mathList = MTMathListBuilder.build(fromString: latex, error: &error), error == nil,
+              let displayList = MTTypesetter.createLineForMathList(mathList, font: font, style: currentStyle) else {
+            return (error, nil)
+        }
+         
+        intrinsicContentSize = intrinsicContentSize(displayList)
+        displayList.textColor = textColor
+        
+        let size = intrinsicContentSize
+        layoutImage(size: size, displayList: displayList)
+        
+        #if os(iOS)
+            let renderer = UIGraphicsImageRenderer(size: size)
+            let image = renderer.image { rendererContext in
+                rendererContext.cgContext.saveGState()
+                rendererContext.cgContext.concatenate(.flippedVertically(size.height))
+                displayList.draw(rendererContext.cgContext)
+                rendererContext.cgContext.restoreGState()
+            }
+            return (nil, image)
+        #endif
+        #if os(macOS)
+            let image = NSImage(size: size, flipped: true) { bounds in
+                guard let context = NSGraphicsContext.current?.cgContext else { return false }
+                context.saveGState()
+                displayList.draw(context)
+                context.restoreGState()
+                return true
+            }
+            return (nil, image)
+        #endif
+    }
+}
+private extension CGAffineTransform {
+    static func flippedVertically(_ height: CGFloat) -> CGAffineTransform {
+        var transform = CGAffineTransform(scaleX: 1, y: -1)
+        transform = transform.translatedBy(x: 0, y: -height)
+        return transform
+    }
+}