LegacyImage.cs

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namespace Engine.Media {
    public class LegacyImage {
        public readonly int Width;
 
        public readonly int Height;
 
        public readonly Color[] Pixels;
 
        public LegacyImage(LegacyImage image) {
            ArgumentNullException.ThrowIfNull(image);
            Width = image.Width;
            Height = image.Height;
            Pixels = (Color[])image.Pixels.Clone();
        }
 
        public LegacyImage(Image image) {
            ArgumentNullException.ThrowIfNull(image);
            Width = image.Width;
            Height = image.Height;
            Pixels = (Color[])image.Pixels.Clone();
        }
 
        public LegacyImage(int width, int height) {
            ArgumentOutOfRangeException.ThrowIfNegative(width);
            ArgumentOutOfRangeException.ThrowIfNegative(height);
            Width = width;
            Height = height;
            Pixels = new Color[width * height];
        }
 
        public Color GetPixel(int x, int y) => x < 0 || x >= Width ? throw new ArgumentOutOfRangeException(nameof(x)) :
            y < 0 || y >= Height ? throw new ArgumentOutOfRangeException(nameof(y)) : Pixels[x + y * Width];
 
        public void SetPixel(int x, int y, Color color) {
            if (x < 0
                || x >= Width) {
                throw new ArgumentOutOfRangeException(nameof(x));
            }
            if (y < 0
                || y >= Height) {
                throw new ArgumentOutOfRangeException(nameof(y));
            }
            Pixels[x + y * Width] = color;
        }
 
        public static void PremultiplyAlpha(LegacyImage image) {
            for (int i = 0; i < image.Pixels.Length; i++) {
                image.Pixels[i] = Color.PremultiplyAlpha(image.Pixels[i]);
            }
        }
 
        public static IEnumerable<LegacyImage> GenerateMipmaps(LegacyImage image, int maxLevelsCount = int.MaxValue) {
            ArgumentNullException.ThrowIfNull(image);
            ArgumentOutOfRangeException.ThrowIfNegative(maxLevelsCount);
            if (maxLevelsCount == 0) {
                yield break;
            }
            int mipWidth = image.Width;
            int mipHeight = image.Height;
            yield return image;
            int level = 1;
            while (true) {
                if (level >= maxLevelsCount) {
                    yield break;
                }
                if ((mipWidth > 1 && mipWidth % 2 != 0)
                    || (mipHeight > 1 && mipHeight % 2 != 0)) {
                    break;
                }
                int num = mipWidth;
                int num2 = mipHeight;
                mipWidth = MathUtils.Max(num / 2, 1);
                mipHeight = MathUtils.Max(num2 / 2, 1);
                LegacyImage mipImage = new(mipWidth, mipHeight);
                int num3 = num / mipWidth;
                int num4 = num2 / mipHeight;
                if (num3 == 2
                    && num4 == 2) {
                    int i = 0;
                    int num5 = 0;
                    for (; i < mipHeight; i++) {
                        int num6 = i * 2 * num;
                        int num7 = 0;
                        while (num7 < mipWidth) {
                            Color color = image.Pixels[num6];
                            Color color2 = image.Pixels[num6 + 1];
                            Color color3 = image.Pixels[num6 + num];
                            Color color4 = image.Pixels[num6 + num + 1];
                            byte r = (byte)((color.R + color2.R + color3.R + color4.R + 2) / 4);
                            byte g = (byte)((color.G + color2.G + color3.G + color4.G + 2) / 4);
                            byte b = (byte)((color.B + color2.B + color3.B + color4.B + 2) / 4);
                            byte a = (byte)((color.A + color2.A + color3.A + color4.A + 2) / 4);
                            mipImage.Pixels[num5] = new Color(r, g, b, a);
                            num7++;
                            num6 += 2;
                            num5++;
                        }
                    }
                }
                else if (num3 == 2
                    && num4 == 1) {
                    int j = 0;
                    int num8 = 0;
                    for (; j < mipHeight; j++) {
                        int num9 = j * num;
                        int num10 = 0;
                        while (num10 < mipWidth) {
                            Color color5 = image.Pixels[num9];
                            Color color6 = image.Pixels[num9 + 1];
                            byte r2 = (byte)((color5.R + color6.R + 1) / 2);
                            byte g2 = (byte)((color5.G + color6.G + 1) / 2);
                            byte b2 = (byte)((color5.B + color6.B + 1) / 2);
                            byte a2 = (byte)((color5.A + color6.A + 1) / 2);
                            mipImage.Pixels[num8] = new Color(r2, g2, b2, a2);
                            num10++;
                            num9 += 2;
                            num8++;
                        }
                    }
                }
                else {
                    if (num3 != 1
                        || num4 != 2) {
                        yield break;
                    }
                    int k = 0;
                    int num11 = 0;
                    for (; k < mipHeight; k++) {
                        int num12 = k * 2 * num;
                        int num13 = 0;
                        while (num13 < mipWidth) {
                            Color color7 = image.Pixels[num12];
                            Color color8 = image.Pixels[num12 + num];
                            byte r3 = (byte)((color7.R + color8.R + 1) / 2);
                            byte g3 = (byte)((color7.G + color8.G + 1) / 2);
                            byte b3 = (byte)((color7.B + color8.B + 1) / 2);
                            byte a3 = (byte)((color7.A + color8.A + 1) / 2);
                            mipImage.Pixels[num11] = new Color(r3, g3, b3, a3);
                            num13++;
                            num12++;
                            num11++;
                        }
                    }
                }
                yield return mipImage;
                image = mipImage;
                int num14 = level + 1;
                level = num14;
            }
            throw new InvalidOperationException(
                "Generating mipmaps with not 2:1 scaling is not supported. Limit mipmap levels count using maxLevelsCount parameter."
            );
        }
 
        public static ImageFileFormat DetermineFileFormat(string extension) => Image.DetermineFileFormat(extension);
 
        public static ImageFileFormat DetermineFileFormat(Stream stream) => Image.DetermineFileFormat(stream);
 
        public static LegacyImage Load(Stream stream, ImageFileFormat format) => new(Image.Load(stream, format));
 
        public static LegacyImage Load(string fileName, ImageFileFormat format) {
            using (Stream stream = Storage.OpenFile(fileName, OpenFileMode.Read)) {
                return Load(stream, format);
            }
        }
 
        public static LegacyImage Load(Stream stream) => new(Image.Load(stream));
 
        public static LegacyImage Load(string fileName) {
            using (Stream stream = Storage.OpenFile(fileName, OpenFileMode.Read)) {
                return Load(stream);
            }
        }
 
        public static void Save(LegacyImage image, Stream stream, ImageFileFormat format, bool saveAlpha) =>
            Image.Save(new Image(image), stream, format, saveAlpha);
 
        public static void Save(LegacyImage image, string fileName, ImageFileFormat format, bool saveAlpha) {
            using (Stream stream = Storage.OpenFile(fileName, OpenFileMode.Create)) {
                Save(image, stream, format, saveAlpha);
            }
        }
    }
}