SwapColors.cs
//
// This code is part of GrapeCity Documents for Imaging samples.
// Copyright (c) GrapeCity, Inc. All rights reserved.
//
using System;
using System.IO;
using System.Drawing;
using System.Collections.Generic;
using System.Linq;
using System.Numerics;
using GrapeCity.Documents.Drawing;
using GrapeCity.Documents.Text;
using GrapeCity.Documents.Imaging;

namespace GcImagingWeb.Samples
{
    // This sample demonstrates how to swap color channels on an image
    // using pixel access. Here we swap red and blue channels to
    // change the way the image looks.
    public class SwapColors
    {
        public GcBitmap GenerateImage(int pixelWidth = 1024, int pixelHeight = 1024, bool opaque = true, float dpiX = 96, float dpiY = 96)
        {
            var bmp = new GcBitmap(pixelWidth, pixelHeight, opaque, dpiX, dpiY);
            using (var bmpSrc = new GcBitmap(Path.Combine("Resources", "ImagesBis", "alpamayo-sq.jpg")))
            {
                // BitBlt requires the opacity of both images to be the same:
                bmpSrc.Opaque = opaque;
                // Render source image onto the target bitmap
                // (generally we might want to resize the source image first,
                // but in this case we just know that the source image has
                // the same size as the target, so skip this step):
                bmp.BitBlt(bmpSrc, 0, 0);

                using (var g = bmp.CreateGraphics())
                {
                    for (int i = 0; i < bmp.PixelWidth; ++i)
                        for (int j = 0; j < bmp.PixelHeight; ++j)
                        {
#if bad_performance // Due to the number of pixels, it is better to optimize pixel operations
                            var color = Color.FromArgb((int)bmp[i, j]);
                            var t = color.B;
                            color = Color.FromArgb(color.A, color.B, color.G, color.R);
                            bmp[i, j] = (uint)color.ToArgb();
#else
                            uint px = bmp[i, j];
                            px = ((px & 0x000000FF) << 16) | ((px & 0x00FF0000) >> 16) | (px & 0xFF00FF00);
                            bmp[i, j] = px;
#endif
                        }
                    // Draw the original image in the bottom right corner for reference:
                    float sx = pixelWidth / 3, sy = pixelHeight / 3;
                    g.DrawImage(bmpSrc, new RectangleF(sx * 2, sy * 2, sx, sy), null, ImageAlign.StretchImage);
                }
            }
            return bmp;
        }
    }
}