What is the best way to know the font size that will result in a specific BlackBox? - What is the best way to know the font size that will result in a specific BlackBox?

Imports Aurigma.GraphicsMill
Imports Aurigma.GraphicsMill.AdvancedDrawing
Imports Aurigma.GraphicsMill.AdvancedDrawing.Art
Imports Aurigma.GraphicsMill.AdvancedDrawing.Effects
Imports Aurigma.GraphicsMill.Codecs
Imports DPointF = System.Drawing.PointF
Imports DRectangleF = System.Drawing.RectangleF

   (...)

    Private Shared Sub UpdateFontSize(options As WarpedTextOptions, graphics As Graphics, targetRect As DRectangleF)

        Dim unionBlackbox As New DRectangleF
        Dim targetRectPixels As New DRectangleF(
                    UnitConverter.ConvertUnitsToPixels(options.DPI, targetRect.X, Unit.Point),
                    UnitConverter.ConvertUnitsToPixels(options.DPI, targetRect.Y, Unit.Point),
                    UnitConverter.ConvertUnitsToPixels(options.DPI, targetRect.Width, Unit.Point),
                    UnitConverter.ConvertUnitsToPixels(options.DPI, targetRect.Height, Unit.Point))

        options.TextFontSize = 1

        Do
            options.TextFontSize = options.TextFontSize + 1

            Dim artText = GetArtText(options, graphics)
            Dim textBlackBox = artText.GetBlackBox()

            Dim shadowBlackbox As New DRectangleF(textBlackBox.Location, textBlackBox.Size)
            shadowBlackbox.Inflate(options.Shadow.SizePixels, options.Shadow.SizePixels)
            shadowBlackbox.Offset(options.Shadow.OffsetXPixels, options.Shadow.OffsetYPixels)

            unionBlackbox = DRectangleF.Union(textBlackBox, shadowBlackbox)

        Loop While unionBlackbox.Width < targetRectPixels.Width AndAlso unionBlackbox.Height < targetRectPixels.Height

        options.TextFontSize = options.TextFontSize - 1

    End Sub

   (...)

	Private Shared Sub UpdateFontSize(
		options As WarpedTextOptions, graphics As Graphics, targetRect As DRectangleF)

		Dim unionBlackbox As New DRectangleF
		Dim targetRectPixels As New DRectangleF(
					UnitConverter.ConvertUnitsToPixels(options.DPI, targetRect.X, Unit.Point),
					UnitConverter.ConvertUnitsToPixels(options.DPI, targetRect.Y, Unit.Point),
					UnitConverter.ConvertUnitsToPixels(options.DPI, targetRect.Width, Unit.Point),
					UnitConverter.ConvertUnitsToPixels(options.DPI, targetRect.Height, Unit.Point))

		'Dim min = MIN_FONT_SIZE
		' 1. The maximum size of inscribed figure is a diagonal of a rectangle
		' 2. Use a font size of the float (Single) type. Otherwise you can get an inaccurate result
		Dim max As Single = System.Math.Sqrt(targetRect.Height * targetRect.Height + targetRect.Width * targetRect.Width)
		'Dim max = targetRect.Height
		Dim max As Single = targetRect.Height

		'options.TextFontSize = min

		' 3. Limit an iteration count to prevent hanging
		Const MAX_ITERATIONS As Integer = 20
		Dim i = 0

		'While min < max
		' 4. Use a condition based on precison
		Const PRECISION As Single = 0.05F

		While (max - min) / max > PRECISION AndAlso i < MAX_ITERATIONS

			' Dim mid As Integer = CInt((min + max) / 2)
			' See p. 2
			Dim mid As Single = CSng((min + max) / 2.0F)

			options.TextFontSize = mid

			Dim artText = GetArtText(options, graphics)
			Dim textBlackBox = artText.GetBlackBox()

			Dim shadowBlackbox As New DRectangleF(textBlackBox.Location, textBlackBox.Size)
			shadowBlackbox.Inflate(options.Shadow.SizePixels, options.Shadow.SizePixels)
			shadowBlackbox.Offset(options.Shadow.OffsetXPixels, options.Shadow.OffsetYPixels)

			unionBlackbox = DRectangleF.Union(textBlackBox, shadowBlackbox)

			' 5. There is no need to increment/decrement the mid value:
			If (unionBlackbox.Width < targetRectPixels.Width AndAlso
				unionBlackbox.Height < targetRectPixels.Height) Then
				'min = mid + 1
				min = mid
			Else
				'max = mid - 1
				max = mid
			End If

			i = i + 1
		End While

	End Sub