How to draw a one-pixel line??
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From: Loren Pechtel on 3 Nov 2009 23:59 I'm having trouble with what seems to be a simple task: I'm trying to draw some vector images on a field of tiles. The tiles are always of integer sizes and can zoom over any reasonable range of values. The images themselves are vector images but they don't simply scale up, as the tile gets bigger more detail is added. (Yeah, I know I'll have to handle printing a bit differently.) The problem I'm having is with images composed entirely of vertical and horizontal lines, black on a gray field. The horizontal lines are fine, I get exactly what I want. Vertical lines aren't working too well, though. A lone vertical line is good enough--two pixels of dark gray instead of one of black but it looks close enough I didn't even realize it was wrong until I got digging into the case that's awful: I have some stripes, some are black/background/background and others are black/background. With antialiasing on the ones with the black every three look fuzzy and the closer ones just look like a blurry blob. With it turned off I'm getting a very clear image, albeit very wrong: The three-step one produces dark gray/dark gray/background and the two-step one simply produces a box of dark gray. Everything is being drawn on a bitmap that is then put in a picturebox. The picturebox is in a panel that fills the form other than a few controls on the right for manipulating the view. The behavior would make sense if somehow I was drawing between pixels on the y axis but all the DrawLines are being fed integer coordinates.
From: Peter Duniho on 4 Nov 2009 02:02 Loren Pechtel wrote: > [...] > The behavior would make sense if somehow I was drawing between pixels > on the y axis but all the DrawLines are being fed integer coordinates. With no scaling/transformation whatsoever? And you are displaying the images also without any scaling or transformation of any sort? How are you determining what the exact pixel values are? Your description sounds as though you're drawing on fractional coordinates, in spite of your statement that you're not. But it's also possible you're simply not gathering your data correctly and that the pixels in the bitmap aren't what you think. Without a concise-but-complete code example that reliably demonstrates the problem, it's practically impossible to understand for sure what problem you're seeing, never mind know what the fix would be. For what it's worth, I tried to reproduce the issue you seem to be describing, and couldn't. When I start with an all-gray bitmap and draw vertical lines into it spaced at various intervals, I always get pixels exactly the color I drew where the lines are, with the original background color where no lines were drawn. See below for a concise(ish)-but-complete code example demonstrating my test. Pete using System; using System.Windows.Forms; using System.Text; using System.Drawing; namespace TestVerticalLineDrawingSingleFile { static class Program { /// <summary> /// The main entry point for the application. /// </summary> [STAThread] static void Main() { Application.EnableVisualStyles(); Application.SetCompatibleTextRenderingDefault(false); Application.Run(new Form1()); } } public class Form1 : Form { private Image _img; private Timer _timerBitmap = new Timer(); private Timer _timerRGB = new Timer(); public Form1() { InitializeComponent(); _UpdateImage(); _UpdatePixelRGB(); _timerBitmap.Interval = 1000; _timerBitmap.Tick += (sender, e) => { _timerBitmap.Enabled = false; _UpdateImage(); }; _timerRGB.Interval = 1500; _timerRGB.Tick += (sender, e) => { _timerRGB.Enabled = false; _UpdatePixelRGB(); }; textBox1.TextChanged += (sender, obj) => _ResetTimer(_timerBitmap); textBox2.TextChanged += (sender, obj) => _ResetTimer(_timerBitmap); textBox3.TextChanged += (sender, obj) => _ResetTimer(_timerRGB); } private void _UpdateImage() { Image imgNew = new Bitmap(128, 128); using (Graphics gfx = Graphics.FromImage(imgNew)) { int dx; if (!int.TryParse(textBox1.Text, out dx)) { dx = 1; textBox1.Text = dx.ToString(); } //gfx.PixelOffsetMode = System.Drawing.Drawing2D.PixelOffsetMode.None; gfx.Clear(Color.Gray); for (int x = 0; x < imgNew.Width; x += dx) { gfx.DrawLine(Pens.Black, x, 0, x, imgNew.Height); } } pictureBox1.Image = imgNew; if (_img != null) { _img.Dispose(); } _img = imgNew; int zoom; if (!int.TryParse(textBox2.Text, out zoom)) { zoom = 100; textBox2.Text = zoom.ToString(); } pictureBox1.Width = imgNew.Width * zoom / 100; pictureBox1.Height = imgNew.Height * zoom / 100; _UpdatePixelRGB(); } private void _ResetTimer(Timer timer) { if (timer.Enabled) { timer.Enabled = false; } timer.Enabled = true; } private void _UpdatePixelRGB() { StringBuilder sb = new StringBuilder(textBox3.Text.Length); foreach (char ch in textBox3.Text) { if (Char.IsDigit(ch) || ch == ',') { sb.Append(ch); } } string[] rgstrCoords = sb.ToString().Split(','); int x, y; if (rgstrCoords.Length != 2 || !int.TryParse(rgstrCoords[0], out x) || !int.TryParse(rgstrCoords[1], out y)) { x = y = 0; textBox3.Text = string.Format("{0},{1}", x.ToString(), y.ToString()); } Color color = ((Bitmap)_img).GetPixel(x, y); label5.Text = string.Format("({3}, {4}) R: {0}, G: {1}, B: {2}", color.R.ToString(), color.G.ToString(), color.B.ToString(), x.ToString(), y.ToString()); } /// <summary> /// Required designer variable. /// </summary> private System.ComponentModel.IContainer components = null; /// <summary> /// Clean up any resources being used. /// </summary> /// <param name="disposing">true if managed resources should be disposed; otherwise, false.</param> protected override void Dispose(bool disposing) { if (disposing && (components != null)) { components.Dispose(); } base.Dispose(disposing); } #region Windows Form Designer generated code /// <summary> /// Required method for Designer support - do not modify /// the contents of this method with the code editor. /// </summary> private void InitializeComponent() { this.label1 = new System.Windows.Forms.Label(); this.textBox1 = new System.Windows.Forms.TextBox(); this.panel1 = new System.Windows.Forms.Panel(); this.textBox2 = new System.Windows.Forms.TextBox(); this.label2 = new System.Windows.Forms.Label(); this.pictureBox1 = new System.Windows.Forms.PictureBox(); this.label3 = new System.Windows.Forms.Label(); this.textBox3 = new System.Windows.Forms.TextBox(); this.label4 = new System.Windows.Forms.Label(); this.label5 = new System.Windows.Forms.Label(); this.panel1.SuspendLayout(); ((System.ComponentModel.ISupportInitialize)(this.pictureBox1)).BeginInit(); this.SuspendLayout(); // // label1 // this.label1.AutoSize = true; this.label1.Location = new System.Drawing.Point(13, 13); this.label1.Name = "label1"; this.label1.Size = new System.Drawing.Size(68, 13); this.label1.TabIndex = 0; this.label1.Text = "Line Interval:"; // // textBox1 // this.textBox1.Location = new System.Drawing.Point(87, 10); this.textBox1.Name = "textBox1"; this.textBox1.Size = new System.Drawing.Size(100, 20); this.textBox1.TabIndex = 1; this.textBox1.Text = "1"; // // panel1 // this.panel1.Anchor = ((System.Windows.Forms.AnchorStyles)((((System.Windows.Forms.AnchorStyles.Top | System.Windows.Forms.AnchorStyles.Bottom) | System.Windows.Forms.AnchorStyles.Left) | System.Windows.Forms.AnchorStyles.Right))); this.panel1.AutoScroll = true; this.panel1.Controls.Add(this.pictureBox1); this.panel1.Location = new System.Drawing.Point(12, 63); this.panel1.Name = "panel1"; this.panel1.Size = new System.Drawing.Size(370, 267); this.panel1.TabIndex = 2; // // textBox2 // this.textBox2.Location = new System.Drawing.Point(87, 37); this.textBox2.Name = "textBox2"; this.textBox2.Size = new System.Drawing.Size(100, 20); this.textBox2.TabIndex = 3; this.textBox2.Text = "100"; // // label2 // this.label2.AutoSize = true; this.label2.Location = new System.Drawing.Point(4, 40); this.label2.Name = "label2"; this.label2.Size = new System.Drawing.Size(77, 13); this.label2.TabIndex = 4; this.label2.Text = "Zoom Percent:"; // // pictureBox1 // this.pictureBox1.Location = new System.Drawing.Point(0, 0); this.pictureBox1.Name = "pictureBox1"; this.pictureBox1.Size = new System.Drawing.Size(100, 50); this.pictureBox1.SizeMode = System.Windows.Forms.PictureBoxSizeMode.StretchImage; this.pictureBox1.TabIndex = 0; this.pictureBox1.TabStop = false; // // label3 // this.label3.AutoSize = true; this.label3.Location = new System.Drawing.Point(218, 13); this.label3.Name = "label3"; this.label3.Size = new System.Drawing.Size(32, 13); this.label3.TabIndex = 5; this.label3.Text = "Pixel:"; // // textBox3 // this.textBox3.Location = new System.Drawing.Point(256, 10); this.textBox3.Name = "textBox3"; this.textBox3.Size = new System.Drawing.Size(100, 20); this.textBox3.TabIndex = 6; this.textBox3.Text = "0,0"; // // label4 // this.label4.AutoSize = true; this.label4.Location = new System.Drawing.Point(218, 37); this.label4.Name = "label4"; this.label4.Size = new System.Drawing.Size(33, 13); this.label4.TabIndex = 7; this.label4.Text = "RGB:"; // // label5 // this.label5.AutoSize = true; this.label5.Location = new System.Drawing.Point(257, 37); this.label5.Name = "label5"; this.label5.Size = new System.Drawing.Size(35, 13); this.label5.TabIndex = 8; this.label5.Text = "label5"; // // Form1 // this.AutoScaleDimensions = new System.Drawing.SizeF(6F, 13F); this.AutoScaleMode = System.Windows.Forms.AutoScaleMode.Font; this.ClientSize = new System.Drawing.Size(394, 342); this.Controls.Add(this.label5); this.Controls.Add(this.label4); this.Controls.Add(this.textBox3); this.Controls.Add(this.label3); this.Controls.Add(this.label2); this.Controls.Add(this.textBox2); this.Controls.Add(this.panel1); this.Controls.Add(this.textBox1); this.Controls.Add(this.label1); this.Name = "Form1"; this.Text = "Form1"; this.panel1.ResumeLayout(false); ((System.ComponentModel.ISupportInitialize)(this.pictureBox1)).EndInit(); this.ResumeLayout(false); this.PerformLayout(); } #endregion private System.Windows.Forms.Label label1; private System.Windows.Forms.TextBox textBox1; private System.Windows.Forms.Panel panel1; private System.Windows.Forms.PictureBox pictureBox1; private System.Windows.Forms.TextBox textBox2; private System.Windows.Forms.Label label2; private System.Windows.Forms.Label label3; private System.Windows.Forms.TextBox textBox3; private System.Windows.Forms.Label label4; private System.Windows.Forms.Label label5; } }
From: Geoffrey Summerhayes on 4 Nov 2009 09:06 On Nov 3, 11:59 pm, Loren Pechtel <lorenpech...(a)hotmail.invalid.com> wrote: > I'm having trouble with what seems to be a simple task: > > I'm trying to draw some vector images on a field of tiles. The tiles > are always of integer sizes and can zoom over any reasonable range of > values. > > The images themselves are vector images but they don't simply scale > up, as the tile gets bigger more detail is added. (Yeah, I know I'll > have to handle printing a bit differently.) > > The problem I'm having is with images composed entirely of vertical > and horizontal lines, black on a gray field. > > The horizontal lines are fine, I get exactly what I want. Vertical > lines aren't working too well, though. A lone vertical line is good > enough--two pixels of dark gray instead of one of black but it looks > close enough I didn't even realize it was wrong until I got digging > into the case that's awful: > > I have some stripes, some are black/background/background and others > are black/background. > > With antialiasing on the ones with the black every three look fuzzy > and the closer ones just look like a blurry blob. > > With it turned off I'm getting a very clear image, albeit very wrong: > The three-step one produces dark gray/dark gray/background and the > two-step one simply produces a box of dark gray. > > Everything is being drawn on a bitmap that is then put in a > picturebox. The picturebox is in a panel that fills the form other > than a few controls on the right for manipulating the view. > > The behavior would make sense if somehow I was drawing between pixels > on the y axis but all the DrawLines are being fed integer coordinates. My psychic powers must be off today, everything is blurry. Can't see the code, the size of the bitmap, the size of the picturebox, properties of the picturebox, the comments in the code, in fact, even the code! On a guess, try making the window 1 pixel wider, see if anything changes. -- Geoff
From: Jeff Johnson on 4 Nov 2009 09:42 "Loren Pechtel" <lorenpechtel(a)hotmail.invalid.com> wrote in message news:%23edaYuQXKHA.1280(a)TK2MSFTNGP04.phx.gbl... When you create the Pen you're using to draw your line are you passing a value of -1 for the width? If not, do so.
From: vanderghast on 4 Nov 2009 10:57
You may get that kind of problem with some LCD monitors while being not in the recommended resolution and, in those cases, that is a problem related to hardware and your choice of resolution. As usual, your problem may be something else, though. Vanderghast, Access MVP "Loren Pechtel" <lorenpechtel(a)hotmail.invalid.com> wrote in message news:%23edaYuQXKHA.1280(a)TK2MSFTNGP04.phx.gbl... > I'm having trouble with what seems to be a simple task: > > I'm trying to draw some vector images on a field of tiles. The tiles > are always of integer sizes and can zoom over any reasonable range of > values. > > The images themselves are vector images but they don't simply scale > up, as the tile gets bigger more detail is added. (Yeah, I know I'll > have to handle printing a bit differently.) > > The problem I'm having is with images composed entirely of vertical > and horizontal lines, black on a gray field. > > The horizontal lines are fine, I get exactly what I want. Vertical > lines aren't working too well, though. A lone vertical line is good > enough--two pixels of dark gray instead of one of black but it looks > close enough I didn't even realize it was wrong until I got digging > into the case that's awful: > > I have some stripes, some are black/background/background and others > are black/background. > > With antialiasing on the ones with the black every three look fuzzy > and the closer ones just look like a blurry blob. > > With it turned off I'm getting a very clear image, albeit very wrong: > The three-step one produces dark gray/dark gray/background and the > two-step one simply produces a box of dark gray. > > Everything is being drawn on a bitmap that is then put in a > picturebox. The picturebox is in a panel that fills the form other > than a few controls on the right for manipulating the view. > > The behavior would make sense if somehow I was drawing between pixels > on the y axis but all the DrawLines are being fed integer coordinates. |