Better transparency handling

Former-commit-id: a1d0f5d52b21aa76531f86ee63f75973311e1837
Former-commit-id: b3f3963a089a4c99ae8ceda8b4ad019b19e32ec2
Former-commit-id: eb5b4e013f56035cd961b03e213cea128ee5e88b

src/ImageProcessor/Colors/Color.cs

@@ -350,9 +350,13 @@ namespace ImageProcessor
         {
             amount = amount.Clamp(0f, 1f);
 
+            if (Math.Abs(from.A - 1) < Epsilon || Math.Abs(from.A) < Epsilon)
+            {
+                return from + (to - from) * amount;
+            }
+
             // Premultiplied.
-            return from + (to - from) * amount;
-            //return (from * (1 - amount)) + to;
+            return from * (1 - amount) + to;
         }
 
         /// <summary>

src/ImageProcessor/Filters/BackgroundColor.cs

@@ -5,6 +5,7 @@
 
 namespace ImageProcessor.Filters
 {
+    using System;
     using System.Threading.Tasks;
 
     /// <summary>
@@ -12,6 +13,11 @@ namespace ImageProcessor.Filters
     /// </summary>
     public class BackgroundColor : ParallelImageProcessor
     {
+        /// <summary>
+        /// The epsilon for comparing floating point numbers.
+        /// </summary>
+        private const float Epsilon = 0.001f;
+
         /// <summary>
         /// Initializes a new instance of the <see cref="BackgroundColor"/> class.
         /// </summary>
@@ -46,11 +52,16 @@ namespace ImageProcessor.Filters
                         {
                             Color color = source[x, y];
 
-                            if (color.A < 1)
+                            if (color.A < 1 && color.A > 0)
                             {
                                 color = Color.Lerp(color, backgroundColor, .5f);
                             }
 
+                            if (Math.Abs(color.A) < Epsilon)
+                            {
+                                color = backgroundColor;
+                            }
+
                             target[x, y] = color;
                         }
                     }

src/ImageProcessor/Filters/ColorMatrix/Polaroid.cs

@@ -33,7 +33,7 @@ namespace ImageProcessor.Filters
         protected override void AfterApply(ImageBase source, ImageBase target, Rectangle targetRectangle, Rectangle sourceRectangle)
         {
             new Vignette { Color = new Color(102 / 255f, 34 / 255f, 0) }.Apply(target, target, targetRectangle);
-            new Glow { Color = new Color(1, 153 / 255f, 102 / 255f) }.Apply(target, target, targetRectangle);
+            new Glow { Color = new Color(1, 153 / 255f, 102 / 255f, .7f) }.Apply(target, target, targetRectangle);
         }
     }
 }

src/ImageProcessor/Filters/Glow.cs

@@ -34,7 +34,7 @@ namespace ImageProcessor.Filters
         {
             int startX = sourceRectangle.X;
             int endX = sourceRectangle.Right;
-            Color color = this.Color;
+            Color glowColor = this.Color;
             Vector2 centre = Rectangle.Center(targetRectangle).ToVector2();
             float rX = this.RadiusX > 0 ? this.RadiusX : targetRectangle.Width / 2f;
             float rY = this.RadiusY > 0 ? this.RadiusY : targetRectangle.Height / 2f;
@@ -49,7 +49,7 @@ namespace ImageProcessor.Filters
                         {
                             float distance = Vector2.Distance(centre, new Vector2(x, y));
                             Color sourceColor = target[x, y];
-                            target[x, y] = Color.Lerp(color, sourceColor, 4f * distance / maxDistance);
+                            target[x, y] = Color.Lerp(sourceColor, glowColor, .334f * (1 - distance / maxDistance));
                         }
                     });
         }

src/ImageProcessor/Filters/Vignette.cs

@@ -17,7 +17,7 @@ namespace ImageProcessor.Filters
         /// <summary>
         /// Gets or sets the vignette color to apply.
         /// </summary>
-        public Color Color { get; set; } = Color.Black;
+        public Color Color { get; set; } = new Color(0, 0, 0, 1);
 
         /// <summary>
         /// Gets or sets the the x-radius.
@@ -34,7 +34,7 @@ namespace ImageProcessor.Filters
         {
             int startX = sourceRectangle.X;
             int endX = sourceRectangle.Right;
-            Color color = this.Color;
+            Color vignetteColor = this.Color;
             Vector2 centre = Rectangle.Center(targetRectangle).ToVector2();
             float rX = this.RadiusX > 0 ? this.RadiusX : targetRectangle.Width / 2f;
             float rY = this.RadiusY > 0 ? this.RadiusY : targetRectangle.Height / 2f;
@@ -49,7 +49,14 @@ namespace ImageProcessor.Filters
                         {
                             float distance = Vector2.Distance(centre, new Vector2(x, y));
                             Color sourceColor = target[x, y];
-                            target[x, y] = Color.Lerp(sourceColor, color, .9f * distance / maxDistance);
+                            //if (sourceColor.A > 0)
+                            //{
+                            target[x, y] = Color.Lerp(sourceColor, vignetteColor, .9f * distance / maxDistance);
+                            //}
+                            //else
+                            //{
+                            //    target[x, y] = Color.Lerp(sourceColor, color, distance / maxDistance);
+                            //}
                         }
                     });
         }

src/ImageProcessor/Formats/Bmp/BmpEncoder.cs

@@ -14,11 +14,6 @@ namespace ImageProcessor.Formats
     /// <remarks>The encoder can currently only write 24-bit rgb images to streams.</remarks>
     public class BmpEncoder : IImageEncoder
     {
-        /// <summary>
-        /// The the transparency threshold.
-        /// </summary>
-        private int threshold = 128;
-
         /// <summary>
         /// Gets or sets the quality of output for images.
         /// </summary>
@@ -31,15 +26,6 @@ namespace ImageProcessor.Formats
         /// <inheritdoc/>
         public string Extension => "bmp";
 
-        /// <summary>
-        /// Gets or sets the transparency threshold.
-        /// </summary>
-        public int Threshold
-        {
-            get { return this.threshold; }
-            set { this.threshold = value.Clamp(0, 255); }
-        }
-
         /// <inheritdoc/>
         public bool IsSupportedFileExtension(string extension)
         {
@@ -132,11 +118,6 @@ namespace ImageProcessor.Formats
 
                     Bgra32 color = Color.ToNonPremultiplied(new Color(r, g, b, a));
 
-                    if (color.A < this.Threshold)
-                    {
-                        color = new Bgra32(0, 0, 0, 0);
-                    }
-
                     writer.Write(color.B);
                     writer.Write(color.G);
                     writer.Write(color.R);

src/ImageProcessor/Formats/Gif/GifEncoder.cs

@@ -15,11 +15,6 @@ namespace ImageProcessor.Formats
     /// </summary>
     public class GifEncoder : IImageEncoder
     {
-        /// <summary>
-        /// The the transparency threshold.
-        /// </summary>
-        private int threshold = 128;
-
         /// <summary>
         /// Gets or sets the quality of output for images.
         /// </summary>
@@ -32,15 +27,6 @@ namespace ImageProcessor.Formats
         /// <inheritdoc/>
         public string MimeType => "image/gif";
 
-        /// <summary>
-        /// Gets or sets the transparency threshold.
-        /// </summary>
-        public int Threshold
-        {
-            get { return this.threshold; }
-            set { this.threshold = value.Clamp(0, 255); }
-        }
-
         /// <inheritdoc/>
         public bool IsSupportedFileExtension(string extension)
         {
@@ -138,7 +124,7 @@ namespace ImageProcessor.Formats
         private QuantizedImage WriteColorTable(ImageBase image, Stream stream, int quality, int bitDepth)
         {
             // Quantize the image returning a pallete.
-            IQuantizer quantizer = new OctreeQuantizer(quality.Clamp(1, 255), bitDepth) { Threshold = this.threshold };
+            IQuantizer quantizer = new OctreeQuantizer(quality.Clamp(1, 255), bitDepth);
             QuantizedImage quantizedImage = quantizer.Quantize(image);
 
             // Grab the pallete and write it to the stream.

src/ImageProcessor/Formats/Gif/Quantizer/OctreeQuantizer.cs

@@ -24,11 +24,6 @@ namespace ImageProcessor.Formats
         /// </summary>
         private readonly int maxColors;
 
-        /// <summary>
-        /// The the transparency threshold.
-        /// </summary>
-        private int threshold = 128;
-
         /// <summary>
         /// Initializes a new instance of the <see cref="OctreeQuantizer"/> class.
         /// </summary>
@@ -65,15 +60,6 @@ namespace ImageProcessor.Formats
             this.maxColors = maxColors;
         }
 
-        /// <summary>
-        /// Gets or sets the transparency threshold.
-        /// </summary>
-        public int Threshold
-        {
-            get { return this.threshold; }
-            set { this.threshold = value.Clamp(0, 255); }
-        }
-
         /// <summary>
         /// Process the pixel in the first pass of the algorithm
         /// </summary>
@@ -105,7 +91,7 @@ namespace ImageProcessor.Formats
             byte paletteIndex = (byte)this.maxColors;
 
             // Get the palette index if it's transparency meets criterea.
-            if (pixel.A >= this.Threshold)
+            if (pixel.A > 0)
             {
                 paletteIndex = (byte)this.octree.GetPaletteIndex(pixel);
             }

src/ImageProcessor/Formats/IImageEncoder.cs

@@ -22,11 +22,6 @@ namespace ImageProcessor.Formats
         /// </summary>
         int Quality { get; set; }
 
-        /// <summary>
-        /// Gets or sets the transparency threshold.
-        /// </summary>
-        int Threshold { get; set; }
-
         /// <summary>
         /// Gets the standard identifier used on the Internet to indicate the type of data that a file contains.
         /// </summary>

src/ImageProcessor/Formats/Jpg/JpegEncoder.cs

@@ -21,11 +21,6 @@ namespace ImageProcessor.Formats
         /// </summary>
         private int quality = 100;
 
-        /// <summary>
-        /// The the transparency threshold.
-        /// </summary>
-        private int threshold = 128;
-
         /// <summary>
         /// Gets or sets the quality, that will be used to encode the image. Quality
         /// index must be between 0 and 100 (compression from max to min).
@@ -37,15 +32,6 @@ namespace ImageProcessor.Formats
             set { this.quality = value.Clamp(1, 100); }
         }
 
-        /// <summary>
-        /// Gets or sets the transparency threshold.
-        /// </summary>
-        public int Threshold
-        {
-            get { return this.threshold; }
-            set { this.threshold = value.Clamp(0, 255); }
-        }
-
         /// <inheritdoc/>
         public string MimeType => "image/jpeg";
 
@@ -127,11 +113,6 @@ namespace ImageProcessor.Formats
 
                             Bgra32 color = Color.ToNonPremultiplied(new Color(r, g, b, a));
 
-                            if (color.A < this.Threshold)
-                            {
-                                color = new Bgra32(0, 0, 0, 0);
-                            }
-
                             samples[start] = color.R;
                             samples[start + 1] = color.G;
                             samples[start + 2] = color.B;

src/ImageProcessor/Formats/Png/PngEncoder.cs

@@ -18,11 +18,6 @@ namespace ImageProcessor.Formats
         /// </summary>
         private const int MaxBlockSize = 0xFFFF;
 
-        /// <summary>
-        /// The the transparency threshold.
-        /// </summary>
-        private int threshold;
-
         /// <summary>
         /// Initializes a new instance of the <see cref="PngEncoder"/> class.
         /// </summary>
@@ -37,15 +32,6 @@ namespace ImageProcessor.Formats
         /// <remarks>Png is a lossless format so this is not used in this encoder.</remarks>
         public int Quality { get; set; }
 
-        /// <summary>
-        /// Gets or sets the transparency threshold.
-        /// </summary>
-        public int Threshold
-        {
-            get { return this.threshold; }
-            set { this.threshold = value.Clamp(0, 255); }
-        }
-
         /// <inheritdoc/>
         public string MimeType => "image/png";
 
@@ -342,11 +328,6 @@ namespace ImageProcessor.Formats
 
                     Bgra32 color = Color.ToNonPremultiplied(new Color(r, g, b, a));
 
-                    if (color.A < this.Threshold)
-                    {
-                        color = new Bgra32(0, 0, 0, 0);
-                    }
-
                     data[dataOffset] = color.R;
                     data[dataOffset + 1] = color.G;
                     data[dataOffset + 2] = color.B;

src/ImageProcessor/Samplers/ImageSampleExtensions.cs

@@ -121,7 +121,7 @@ namespace ImageProcessor.Samplers
         /// <returns>The <see cref="Image"/></returns>
         public static Image Rotate(this Image source, float degrees)
         {
-            return source.Process(source.Width, source.Height, source.Bounds, source.Bounds, new Resampler(new RobidouxResampler()) { Angle = degrees });
+            return source.Process(source.Width, source.Height, source.Bounds, source.Bounds, new Resampler(new BicubicResampler()) { Angle = degrees });
         }
 
         /// <summary>

tests/ImageProcessor.Tests/Processors/Filters/FilterTests.cs

@@ -13,39 +13,39 @@ namespace ImageProcessor.Tests
     {
         public static readonly TheoryData<string, IImageProcessor> Filters = new TheoryData<string, IImageProcessor>
         {
-            { "Brightness-50", new Brightness(50) },
-            { "Brightness--50", new Brightness(-50) },
-            { "Contrast-50", new Contrast(50) },
-            { "Contrast--50", new Contrast(-50) },
-            { "BackgroundColor", new BackgroundColor(new Color(243 / 255f, 87 / 255f, 161 / 255f))},
-            { "Blend", new Blend(new Image(File.OpenRead("TestImages/Formats/Bmp/Car.bmp")),50)},
-            { "Saturation-50", new Saturation(50) },
-            { "Saturation--50", new Saturation(-50) },
+            //{ "Brightness-50", new Brightness(50) },
+            //{ "Brightness--50", new Brightness(-50) },
+            //{ "Contrast-50", new Contrast(50) },
+            //{ "Contrast--50", new Contrast(-50) },
+            //{ "BackgroundColor", new BackgroundColor(new Color(243 / 255f, 87 / 255f, 161 / 255f,.5f))},
+            //{ "Blend", new Blend(new Image(File.OpenRead("TestImages/Formats/Bmp/Car.bmp")),50)},
+            //{ "Saturation-50", new Saturation(50) },
+            //{ "Saturation--50", new Saturation(-50) },
             { "Alpha--50", new Alpha(50) },
-            { "Invert", new Invert() },
-            { "Sepia", new Sepia() },
-            { "BlackWhite", new BlackWhite() },
-            { "Lomograph", new Lomograph() },
+            //{ "Invert", new Invert() },
+            //{ "Sepia", new Sepia() },
+            //{ "BlackWhite", new BlackWhite() },
+            //{ "Lomograph", new Lomograph() },
             { "Polaroid", new Polaroid() },
-            { "Kodachrome", new Kodachrome() },
-            { "GreyscaleBt709", new GreyscaleBt709() },
-            { "GreyscaleBt601", new GreyscaleBt601() },
-            { "Kayyali", new Kayyali() },
-            { "Kirsch", new Kirsch() },
-            { "Laplacian3X3", new Laplacian3X3() },
-            { "Laplacian5X5", new Laplacian5X5() },
-            { "LaplacianOfGaussian", new LaplacianOfGaussian() },
-            { "Prewitt", new Prewitt() },
-            { "RobertsCross", new RobertsCross() },
-            { "Scharr", new Scharr() },
-            { "Sobel", new Sobel {Greyscale = true} },
-            { "Pixelate", new Pixelate(8)  },
-            { "GuassianBlur", new GuassianBlur(10) },
-            { "GuassianSharpen", new GuassianSharpen(10) },
-            { "Hue-180", new Hue(180) },
-            { "Hue--180", new Hue(-180) },
-            { "BoxBlur", new BoxBlur(10) },
-            {"Vignette", new Vignette()}
+            //{ "Kodachrome", new Kodachrome() },
+            //{ "GreyscaleBt709", new GreyscaleBt709() },
+            //{ "GreyscaleBt601", new GreyscaleBt601() },
+            //{ "Kayyali", new Kayyali() },
+            //{ "Kirsch", new Kirsch() },
+            //{ "Laplacian3X3", new Laplacian3X3() },
+            //{ "Laplacian5X5", new Laplacian5X5() },
+            //{ "LaplacianOfGaussian", new LaplacianOfGaussian() },
+            //{ "Prewitt", new Prewitt() },
+            //{ "RobertsCross", new RobertsCross() },
+            //{ "Scharr", new Scharr() },
+            //{ "Sobel", new Sobel {Greyscale = true} },
+            //{ "Pixelate", new Pixelate(8)  },
+            //{ "GuassianBlur", new GuassianBlur(10) },
+            //{ "GuassianSharpen", new GuassianSharpen(10) },
+            //{ "Hue-180", new Hue(180) },
+            //{ "Hue--180", new Hue(-180) },
+            //{ "BoxBlur", new BoxBlur(10) },
+            //{"Vignette", new Vignette()}
         };
 
         [Theory]

tests/ImageProcessor.Tests/Processors/Samplers/SamplerTests.cs

@@ -13,20 +13,20 @@
         public static readonly TheoryData<string, IResampler> Samplers =
             new TheoryData<string, IResampler>
             {
-                //{ "Bicubic", new BicubicResampler() },
-                //{ "Triangle", new TriangleResampler() },
-                //{ "Box", new BoxResampler() },
-                //{ "Lanczos3", new Lanczos3Resampler() },
-                //{ "Lanczos5", new Lanczos5Resampler() },
-                //{ "Lanczos8", new Lanczos8Resampler() },
-                //{ "MitchellNetravali", new MitchellNetravaliResampler() },
+                { "Bicubic", new BicubicResampler() },
+                { "Triangle", new TriangleResampler() },
+                { "Box", new BoxResampler() },
+                { "Lanczos3", new Lanczos3Resampler() },
+                { "Lanczos5", new Lanczos5Resampler() },
+                { "Lanczos8", new Lanczos8Resampler() },
+                { "MitchellNetravali", new MitchellNetravaliResampler() },
                 { "NearestNeighbor", new NearestNeighborResampler() },
-                //{ "Hermite", new HermiteResampler() },
-                //{ "Spline", new SplineResampler() },
-                //{ "Robidoux", new RobidouxResampler() },
-                //{ "RobidouxSharp", new RobidouxSharpResampler() },
-                //{ "RobidouxSoft", new RobidouxSoftResampler() },
-                //{ "Welch", new WelchResampler() }
+                { "Hermite", new HermiteResampler() },
+                { "Spline", new SplineResampler() },
+                { "Robidoux", new RobidouxResampler() },
+                { "RobidouxSharp", new RobidouxSharpResampler() },
+                { "RobidouxSoft", new RobidouxSoftResampler() },
+                { "Welch", new WelchResampler() }
             };
 
         public static readonly TheoryData<RotateType, FlipType> RotateFlips = new TheoryData<RotateType, FlipType>
@@ -167,6 +167,7 @@
                     using (FileStream output = File.OpenWrite($"TestOutput/Rotate/{filename}"))
                     {
                         image.Rotate(45, sampler)
+                             .BackgroundColor(Color.Aqua)
                              .Save(output);
                     }