Add base ColorHelpers porting from WinUI

src/Avalonia.Controls/ColorPicker/ColorSpectrum/ColorHelpers.cs

@@ -0,0 +1,388 @@
+// This source file is adapted from the WinUI project.
+// (https://github.com/microsoft/microsoft-ui-xaml)
+//
+// Licensed to The Avalonia Project under the MIT License.
+
+using System;
+using System.Collections.Generic;
+using System.Runtime.InteropServices;
+using Avalonia.Media;
+using Avalonia.Media.Imaging;
+using Avalonia.Platform;
+
+namespace Avalonia.Controls.Primitives
+{
+    internal static class ColorHelpers
+    {
+        public const int CheckerSize = 4;
+
+        public static bool ToDisplayNameExists
+        {
+            get => false;
+        }
+
+        public static string ToDisplayName(Color color)
+        {
+            return string.Empty;
+        }
+
+        public static Hsv IncrementColorChannel(
+            Hsv originalHsv,
+            ColorPickerHsvChannel channel,
+            IncrementDirection direction,
+            IncrementAmount amount,
+            bool shouldWrap,
+            double minBound,
+            double maxBound)
+        {
+            Hsv newHsv = originalHsv;
+
+            if (amount == IncrementAmount.Small || !ToDisplayNameExists)
+            {
+                // In order to avoid working with small values that can incur rounding issues,
+                // we'll multiple saturation and value by 100 to put them in the range of 0-100 instead of 0-1.
+                newHsv.S *= 100;
+                newHsv.V *= 100;
+
+                // Note: *valueToIncrement replaced with ref local variable for C#, must be initialized
+                ref double valueToIncrement = ref newHsv.H;
+                double incrementAmount = 0.0;
+
+                // If we're adding a small increment, then we'll just add or subtract 1.
+                // If we're adding a large increment, then we want to snap to the next
+                // or previous major value - for hue, this is every increment of 30;
+                // for saturation and value, this is every increment of 10.
+                switch (channel)
+                {
+                    case ColorPickerHsvChannel.Hue:
+                        valueToIncrement = ref newHsv.H;
+                        incrementAmount = amount == IncrementAmount.Small ? 1 : 30;
+                        break;
+
+                    case ColorPickerHsvChannel.Saturation:
+                        valueToIncrement = ref newHsv.S;
+                        incrementAmount = amount == IncrementAmount.Small ? 1 : 10;
+                        break;
+
+                    case ColorPickerHsvChannel.Value:
+                        valueToIncrement = ref newHsv.V;
+                        incrementAmount = amount == IncrementAmount.Small ? 1 : 10;
+                        break;
+
+                    default:
+                        throw new InvalidOperationException("Invalid ColorPickerHsvChannel.");
+                }
+
+                double previousValue = valueToIncrement;
+
+                valueToIncrement += (direction == IncrementDirection.Lower ? -incrementAmount : incrementAmount);
+
+                // If the value has reached outside the bounds, we were previous at the boundary, and we should wrap,
+                // then we'll place the selection on the other side of the spectrum.
+                // Otherwise, we'll place it on the boundary that was exceeded.
+                if (valueToIncrement < minBound)
+                {
+                    valueToIncrement = (shouldWrap && previousValue == minBound) ? maxBound : minBound;
+                }
+
+                if (valueToIncrement > maxBound)
+                {
+                    valueToIncrement = (shouldWrap && previousValue == maxBound) ? minBound : maxBound;
+                }
+
+                // We multiplied saturation and value by 100 previously, so now we want to put them back in the 0-1 range.
+                newHsv.S /= 100;
+                newHsv.V /= 100;
+            }
+            else
+            {
+                // While working with named colors, we're going to need to be working in actual HSV units,
+                // so we'll divide the min bound and max bound by 100 in the case of saturation or value,
+                // since we'll have received units between 0-100 and we need them within 0-1.
+                if (channel == ColorPickerHsvChannel.Saturation ||
+                    channel == ColorPickerHsvChannel.Value)
+                {
+                    minBound /= 100;
+                    maxBound /= 100;
+                }
+
+                newHsv = FindNextNamedColor(originalHsv, channel, direction, shouldWrap, minBound, maxBound);
+            }
+
+            return newHsv;
+        }
+
+        public static Hsv FindNextNamedColor(
+            Hsv originalHsv,
+            ColorPickerHsvChannel channel,
+            IncrementDirection direction,
+            bool shouldWrap,
+            double minBound,
+            double maxBound)
+        {
+            // There's no easy way to directly get the next named color, so what we'll do
+            // is just iterate in the direction that we want to find it until we find a color
+            // in that direction that has a color name different than our current color name.
+            // Once we find a new color name, then we'll iterate across that color name until
+            // we find its bounds on the other side, and then select the color that is exactly
+            // in the middle of that color's bounds.
+            Hsv newHsv = originalHsv;
+            
+            string originalColorName = ColorHelpers.ToDisplayName(originalHsv.ToRgb().ToColor());
+            string newColorName = originalColorName;
+
+            // Note: *newValue replaced with ref local variable for C#, must be initialized
+            double originalValue = 0.0;
+            ref double newValue = ref newHsv.H;
+            double incrementAmount = 0.0;
+
+            switch (channel)
+            {
+                case ColorPickerHsvChannel.Hue:
+                    originalValue = originalHsv.H;
+                    newValue = ref newHsv.H;
+                    incrementAmount = 1;
+                    break;
+
+                case ColorPickerHsvChannel.Saturation:
+                    originalValue = originalHsv.S;
+                    newValue = ref newHsv.S;
+                    incrementAmount = 0.01;
+                    break;
+
+                case ColorPickerHsvChannel.Value:
+                    originalValue = originalHsv.V;
+                    newValue = ref newHsv.V;
+                    incrementAmount = 0.01;
+                    break;
+
+                default:
+                    throw new InvalidOperationException("Invalid ColorPickerHsvChannel.");
+            }
+
+            bool shouldFindMidPoint = true;
+
+            while (newColorName == originalColorName)
+            {
+                double previousValue = newValue;
+                newValue += (direction == IncrementDirection.Lower ? -1 : 1) * incrementAmount;
+
+                bool justWrapped = false;
+
+                // If we've hit a boundary, then either we should wrap or we shouldn't.
+                // If we should, then we'll perform that wrapping if we were previously up against
+                // the boundary that we've now hit.  Otherwise, we'll stop at that boundary.
+                if (newValue > maxBound)
+                {
+                    if (shouldWrap)
+                    {
+                        newValue = minBound;
+                        justWrapped = true;
+                    }
+                    else
+                    {
+                        newValue = maxBound;
+                        shouldFindMidPoint = false;
+                        newColorName = ColorHelpers.ToDisplayName(newHsv.ToRgb().ToColor());
+                        break;
+                    }
+                }
+                else if (newValue < minBound)
+                {
+                    if (shouldWrap)
+                    {
+                        newValue = maxBound;
+                        justWrapped = true;
+                    }
+                    else
+                    {
+                        newValue = minBound;
+                        shouldFindMidPoint = false;
+                        newColorName = ColorHelpers.ToDisplayName(newHsv.ToRgb().ToColor());
+                        break;
+                    }
+                }
+
+                if (!justWrapped &&
+                    previousValue != originalValue &&
+                    Math.Sign(newValue - originalValue) != Math.Sign(previousValue - originalValue))
+                {
+                    // If we've wrapped all the way back to the start and have failed to find a new color name,
+                    // then we'll just quit - there isn't a new color name that we're going to find.
+                    shouldFindMidPoint = false;
+                    break;
+                }
+
+                newColorName = ColorHelpers.ToDisplayName(newHsv.ToRgb().ToColor());
+            }
+
+            if (shouldFindMidPoint)
+            {
+                Hsv startHsv = newHsv;
+                Hsv currentHsv = startHsv;
+                double startEndOffset = 0;
+                string currentColorName = newColorName;
+
+                // Note: *startValue/*currentValue replaced with ref local variables for C#, must be initialized
+                ref double startValue = ref startHsv.H;
+                ref double currentValue = ref currentHsv.H;
+                double wrapIncrement = 0;
+
+                switch (channel)
+                {
+                    case ColorPickerHsvChannel.Hue:
+                        startValue = ref startHsv.H;
+                        currentValue = ref currentHsv.H;
+                        wrapIncrement = 360.0;
+                        break;
+
+                    case ColorPickerHsvChannel.Saturation:
+                        startValue = ref startHsv.S;
+                        currentValue = ref currentHsv.S;
+                        wrapIncrement = 1.0;
+                        break;
+
+                    case ColorPickerHsvChannel.Value:
+                        startValue = ref startHsv.V;
+                        currentValue = ref currentHsv.V;
+                        wrapIncrement = 1.0;
+                        break;
+
+                    default:
+                        throw new InvalidOperationException("Invalid ColorPickerHsvChannel.");
+                }
+
+                while (newColorName == currentColorName)
+                {
+                    currentValue += (direction == IncrementDirection.Lower ? -1 : 1) * incrementAmount;
+
+                    // If we've hit a boundary, then either we should wrap or we shouldn't.
+                    // If we should, then we'll perform that wrapping if we were previously up against
+                    // the boundary that we've now hit.  Otherwise, we'll stop at that boundary.
+                    if (currentValue > maxBound)
+                    {
+                        if (shouldWrap)
+                        {
+                            currentValue = minBound;
+                            startEndOffset = maxBound - minBound;
+                        }
+                        else
+                        {
+                            currentValue = maxBound;
+                            break;
+                        }
+                    }
+                    else if (currentValue < minBound)
+                    {
+                        if (shouldWrap)
+                        {
+                            currentValue = maxBound;
+                            startEndOffset = minBound - maxBound;
+                        }
+                        else
+                        {
+                            currentValue = minBound;
+                            break;
+                        }
+                    }
+
+                    currentColorName = ColorHelpers.ToDisplayName(currentHsv.ToRgb().ToColor());
+                }
+
+                newValue = (startValue + currentValue + startEndOffset) / 2;
+
+                // Dividing by 2 may have gotten us halfway through a single step, so we'll
+                // remove that half-step if it exists.
+                double leftoverValue = Math.Abs(newValue);
+
+                while (leftoverValue > incrementAmount)
+                {
+                    leftoverValue -= incrementAmount;
+                }
+
+                newValue -= leftoverValue;
+
+                while (newValue < minBound)
+                {
+                    newValue += wrapIncrement;
+                }
+
+                while (newValue > maxBound)
+                {
+                    newValue -= wrapIncrement;
+                }
+            }
+
+            return newHsv;
+        }
+
+        public static double IncrementAlphaChannel(
+            double originalAlpha,
+            IncrementDirection direction,
+            IncrementAmount amount,
+            bool shouldWrap,
+            double minBound,
+            double maxBound)
+        {
+            // In order to avoid working with small values that can incur rounding issues,
+            // we'll multiple alpha by 100 to put it in the range of 0-100 instead of 0-1.
+            originalAlpha *= 100;
+
+            const double smallIncrementAmount = 1;
+            const double largeIncrementAmount = 10;
+
+            if (amount == IncrementAmount.Small)
+            {
+                originalAlpha += (direction == IncrementDirection.Lower ? -1 : 1) * smallIncrementAmount;
+            }
+            else
+            {
+                if (direction == IncrementDirection.Lower)
+                {
+                    originalAlpha = Math.Ceiling((originalAlpha - largeIncrementAmount) / largeIncrementAmount) * largeIncrementAmount;
+                }
+                else
+                {
+                    originalAlpha = Math.Floor((originalAlpha + largeIncrementAmount) / largeIncrementAmount) * largeIncrementAmount;
+                }
+            }
+
+            // If the value has reached outside the bounds and we should wrap, then we'll place the selection
+            // on the other side of the spectrum.  Otherwise, we'll place it on the boundary that was exceeded.
+            if (originalAlpha < minBound)
+            {
+                originalAlpha = shouldWrap ? maxBound : minBound;
+            }
+
+            if (originalAlpha > maxBound)
+            {
+                originalAlpha = shouldWrap ? minBound : maxBound;
+            }
+
+            // We multiplied alpha by 100 previously, so now we want to put it back in the 0-1 range.
+            return originalAlpha / 100;
+        }
+
+        public static WriteableBitmap CreateBitmapFromPixelData(
+            int pixelWidth,
+            int pixelHeight,
+            List<byte> bgraPixelData)
+        {
+            Vector dpi = new Vector(96, 96); // Standard may need to change on some devices
+
+            WriteableBitmap bitmap = new WriteableBitmap(
+                new PixelSize(pixelWidth, pixelHeight),
+                dpi,
+                PixelFormat.Bgra8888,
+                AlphaFormat.Premul);
+
+            // Warning: This is highly questionable
+            using (var frameBuffer = bitmap.Lock())
+            {
+                Marshal.Copy(bgraPixelData.ToArray(), 0, frameBuffer.Address, bgraPixelData.Count);
+            }
+
+            return bitmap;
+        }
+    }
+}