//// This code is part of Document Solutions for Imaging demos.// Copyright (c) MESCIUS inc. All rights reserved.//using System.IO;using System.Drawing;using GrapeCity.Documents.Drawing;using GrapeCity.Documents.Text;using GrapeCity.Documents.Imaging;using GCTEXT = GrapeCity.Documents.Text;
namespace DsImagingWeb.Demos{    // This sample shows how a color spectrum with fall offs from fully saturated    // colors to white and black can be easily created using linear gradient brushes    // and GcBitmap.Renderer.TransparencyMaskBitmap.    public class ColorSpectrum    {        public GcBitmap GenerateImage(Size pixelSize, float dpi, bool opaque, string[] sampleParams = null)        {            // Color spectrum gradient brush:            var spec = new LinearGradientBrush(Color.Red, Color.Red);            var step = 1f / 6f;            spec.GradientStops = new GradientStop[]            {                new GradientStop(Color.Yellow, step),                new GradientStop(Color.Green, step * 2),                new GradientStop(Color.Cyan, step * 3),                new GradientStop(Color.Blue, step * 4),                new GradientStop(Color.Magenta, step * 5),            };
            // Create the spectrum in a separate temp bitmap:            var spectrumSz = new Size(pixelSize.Width, (int)(pixelSize.Height * 0.75f));            // Falloff brush and mask:            using var tbmp = new GcBitmap(spectrumSz.Width, spectrumSz.Height, true);            using var tgfx = tbmp.CreateGraphics();            // Black is opaque, White transparent:            var falloff = new LinearGradientBrush(Color.Black, PointF.Empty, Color.Black, new PointF(0, 1));            // Additional gray stops provide a more gradual and pleasing appearance:            falloff.GradientStops = new GradientStop[]            {                new GradientStop(Color.LightGray, 0.35f),                new GradientStop(Color.White, 0.5f),                new GradientStop(Color.LightGray, 0.65f)            };            // Fill the mask with the gradient that will define the transparency:            tgfx.FillRectangle(new RectangleF(0, 0, tbmp.Width, tbmp.Height), falloff);            // Convert mask to grayscale for use as the transparency mask:            using var mask = tbmp.ToGrayscaleBitmap();                        // Reuse the original mask bitmap;            // Fill it with a gradient from white at the top to black at the bottom:            var grad = new LinearGradientBrush(Color.White, PointF.Empty, Color.Black, new PointF(0, 1));            tgfx.FillRectangle(new RectangleF(0, 0, spectrumSz.Width, spectrumSz.Height), grad);
            // Add transparency mask and draw the gradient:            tbmp.Renderer.TransparencyMaskBitmap = mask;            tgfx.FillRectangle(new RectangleF(PointF.Empty, spectrumSz), spec);
            // Copy spectrum to the target bitmap:            var bmp = new GcBitmap(pixelSize.Width, pixelSize.Height, true, dpi, dpi);            bmp.BitBlt(tbmp, 0, 0);
            // Add some explanatory texts below the spectrum:            var g = bmp.CreateGraphics();            var rc = new RectangleF(0, spectrumSz.Height, spectrumSz.Width, bmp.PixelHeight - spectrumSz.Height);            var tf = new TextFormat()            {                Font = GCTEXT.Font.FromFile(Path.Combine("Resources", "Fonts", "FreeMonoBold.ttf")),                FontSize = 14,            };            g.FillRectangle(rc, Color.LightGray);            g.DrawString(                "The color spectrum is drawn using a horizontal linear gradient brush with 7 stops:\n" +                "Red - Yellow - Green - Cyan - Blue - Magenta - Red.\n" +                "The background is filled with a vertical gradient from white to black. " +                "A TransparencyMaskBitmap with a vertical gradient that changes from 0 " +                "(opaque) to 1 (transparent) back to 0 (opaque) provides falloffs " +                "from spectrum colors in the center up to white and down to black backgrounds.",                tf, rc, TextAlignment.Center, ParagraphAlignment.Center);
            return bmp;        }    }}