McBitFont/McBitFont/ImageImporter.cs

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.ComponentModel.DataAnnotations;
using System.Data;
using System.Drawing;
using System.Drawing.Drawing2D;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace McBitFont {
    public partial class ImageImporter : Form {

        private int fw, fh, pixelization, threshold;
        private Color[] colorPool = [Color.Black, Color.White];
        private Bitmap bmpOriginal, bmpProcessed;
        public Bitmap bmpScaled;

        public ImageImporter(int width, int height) {
            InitializeComponent();
            fw = width;
            fh = height;
        }

        private void UpdateControls(byte level) {
            switch (level) {
                case 1:
                    bmpProcessed = null;
                    bmpScaled = null;
                    pbProcessed.Image = null;
                    pbScaled.Image = null;
                    lblProcessedSize.Text = "0 x 0";
                    lblScaledSize.Text = "0 x 0";
                    btnResize.Enabled = false;
                    btnOK.Enabled = false;
                    btnConvert.Enabled = true;
                    break;
                case 2:
                    bmpScaled = null;
                    pbScaled.Image = null;
                    lblScaledSize.Text = "0 x 0";
                    btnOK.Enabled = false;
                    btnResize.Enabled = true;
                    break;
                case 3:
                    btnOK.Enabled = true;
                    break;
            }
        }

        private void btnOK_Click(object sender, EventArgs e) {
            DialogResult = DialogResult.OK;
        }

        private void btnCancel_Click(object sender, EventArgs e) {
            DialogResult = DialogResult.Cancel;
        }

        // Pick a color from color pool that is closest to an average of given colors 
        private Color PickColor(Color[] colors) {
            int i;
            int r = 0; int g = 0; int b = 0;

            // Calculating average color amongst givet color set
            for (i = 0; i < colors.Length; i++) {
                r += colors[i].R;
                g += colors[i].G;
                b += colors[i].B;
            }
            r /= colors.Length;
            g /= colors.Length;
            b /= colors.Length;

            int near = 1000;
            int ind = 0;

            // Picking a closts color from color pool
            for (i = 0; i < colorPool.Length; i++) {
                int valR = colorPool[i].R - r + threshold;
                int valG = colorPool[i].R - g + threshold;
                int valB = colorPool[i].R - b + threshold;
                if (valR < 0) valR = -valR;
                if (valG < 0) valG = -valG;
                if (valB < 0) valB = -valB;

                threshold = tbThreshold.Value;
                int total = valR + valG + valB;

                if (total < near) {
                    ind = i;
                    near = total;
                }
            }
            return colorPool[ind];
        }

        private static void DrawArrow(Graphics g, Point from, Point to, float thickness = 1, Color? color = null) {
            if (color == null) color = Color.Black;
            var pen = new Pen((Color)color, thickness) {
                CustomEndCap = new AdjustableArrowCap(4, 5)
            };
            g.DrawLine(pen, from, to);
        }

        private void tbPixelization_ValueChanged(object sender, EventArgs e) {
            lblPixelization.Text = "Pixelization: " + tbPixelization.Value.ToString();
        }

        private void tbThreshold_ValueChanged(object sender, EventArgs e) {
            lblThreshold.Text = "Threshold: " + tbThreshold.Value.ToString();
        }

        private void btnLoadImage_Click(object sender, EventArgs e) {
            if (dlgLoadImage.ShowDialog() == DialogResult.OK) {
                bmpOriginal = new Bitmap(dlgLoadImage.FileName);

                pbOriginal.Image = Draw200x200(bmpOriginal);
                lblOrigSize.Text = bmpOriginal.Width.ToString() + " x " + bmpOriginal.Height.ToString()
                    + " (" + pbOriginal.Image.Width.ToString() + " x " + pbOriginal.Image.Height.ToString() + ")";

                // Clear other images
                UpdateControls(1);
            }
        }

        private void btnConvert_Click(object sender, EventArgs e) {
            pixelization = tbPixelization.Value;
            //Bitmap bmOrig = (Bitmap)pbOriginal.Image;
            bmpProcessed = new Bitmap(bmpOriginal.Width, bmpOriginal.Height);

            // Processing image
            using (Graphics g = Graphics.FromImage(bmpProcessed)) {
                List<Color> block;
                Rectangle rect = new Rectangle();
                SolidBrush sb = new SolidBrush(Color.Black);
                Color final = Color.Black;
                Color pixel;

                // Going through original image with steps = pixelization
                for (int x = 0; x < bmpOriginal.Width; x += pixelization) {
                    for (int y = 0; y < bmpOriginal.Height; y += pixelization) {
                        block = [];

                        // Going throug a block pixel by pixel to calculate its average color later
                        for (int v = 0; v < pixelization; v++) {
                            for (int c = 0; c < pixelization; c++) {
                                if (x + v < bmpOriginal.Width && y + c < bmpOriginal.Height) {
                                    pixel = bmpOriginal.GetPixel(x + v, y + c);
                                    if (pixel.A <= tbTransparency.Value) pixel = Color.White;
                                    block.Add(pixel);
                                }
                            }
                        }

                        // Getting a color from the color pool and painting the block
                        if (block.Count > 0) {
                            final = PickColor(block.ToArray());
                            sb.Color = final;

                            rect.X = x;
                            rect.Y = y;
                            rect.Width = pixelization;
                            rect.Height = pixelization;

                            g.FillRectangle(sb, rect);
                        }
                    }
                }
            }

            pbProcessed.Image = Draw200x200(bmpProcessed);
            lblProcessedSize.Text = bmpProcessed.Width.ToString() + " x " + bmpProcessed.Height.ToString()
                + " (" + pbProcessed.Image.Width.ToString() + " x " + pbProcessed.Image.Height.ToString() + ")";

            UpdateControls(2);
        }

        private void btnResize_Click(object sender, EventArgs e) {
            bmpScaled = DrawScaled(bmpProcessed, fw, fh);

            pbScaled.Image = Draw200x200(bmpScaled);
            lblScaledSize.Text = bmpScaled.Width.ToString() + " x " + bmpScaled.Height.ToString()
                + " (" + pbScaled.Image.Width.ToString() + " x " + pbScaled.Image.Height.ToString() + ")";
            UpdateControls(3);
        }

        // Draw 200x200 bitmap for picturebox
        private static Bitmap Draw200x200(Bitmap bmpRef) {
            return DrawScaled(bmpRef, 200, 200);
        }

        // Draw scaled bitmap keeping aspect ratio
        private static Bitmap DrawScaled(Bitmap bmpRef, int w, int h) {
            var scale = Math.Min(w / (double)bmpRef.Width, h / (double)bmpRef.Height);
            var bmpNew = new Bitmap((int)(bmpRef.Width * scale), (int)(bmpRef.Height * scale));

            using (Graphics g = Graphics.FromImage(bmpNew)) {
                g.InterpolationMode = InterpolationMode.NearestNeighbor;
                g.PixelOffsetMode = PixelOffsetMode.Half;
                g.DrawImage(bmpRef, 0, 0, bmpNew.Width, bmpNew.Height);
            }

            return bmpNew;
        }

        private void tbThreshold_KeyDown(object sender, KeyEventArgs e) {
            if (e.KeyCode == Keys.C) {
                tbThreshold.Value = 0;
            }
        }

        private void tbPixelization_KeyDown(object sender, KeyEventArgs e) {
            if (e.KeyCode == Keys.C) {
                tbPixelization.Value = 1;
            }
        }

        private void tbTransparency_ValueChanged(object sender, EventArgs e) {
            lblTransparency.Text = "Transparency threshold: " + tbTransparency.Value.ToString();
        }

        private void tbTransparency_KeyDown(object sender, KeyEventArgs e) {
            if (e.KeyCode == Keys.C) {
                tbTransparency.Value = 32;
            }
        }

        private void ImageImporter_Paint(object sender, PaintEventArgs e) {
            DrawArrow(e.Graphics, new Point(175, 246), new Point(255, 246), 2, Color.SlateGray);
            DrawArrow(e.Graphics, new Point(380, 246), new Point(455, 246), 2, Color.SlateGray);
        }
    }
}