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Course IPCis: Image Processing with C#
Chapter C1: Commented Code of the Bitmap Project


Copyright © by V. Miszalok, last update: 2010-05-06
using System; //Home of the base class of all classes "System.Object" and of all primitive data types such as Int32, Int16, double, string.
using System.Drawing; //Home of the "Graphics" class and its drawing methods such as DrawStirng, DrawLine, DrawRectangle, FillClosedCurve etc.
using System.Drawing.Imaging; //Home of the Bitmap-class.
using System.Windows.Forms; //Home of the "Form" class (base class of our main window Form1) and its method Application.Run.
Entry public class Form1 : Form
//We derive our window Form1 from the class Form, which the compiler automatically finds in the System.Windows.Forms namespace.
{ [STAThread] [STAThread] static void Main() { Application.Run( new Form1() ); } //Create a single thread instance of Form1 and ask the operating system to start it as main window of our program.
Brush bbrush = SystemBrushes.ControlText; //Create a reference to an already existing Brush object (just a programming shortcut).
Brush rbrush = new SolidBrush( Color.Red ); //Create a new global Brush object.
Bitmap bmp; //Global Bitmap-object
int nClicks; //Global counter of mouse clicks is used to switch through 8 different views of bmp.
Constructor public Form1()
{ MenuItem miRead = new MenuItem( "&Read", new EventHandler( MenuFileRead ) ); //Purpose: Open an image file.
MenuItem miExit = new MenuItem( "&Exit", new EventHandler( MenuFileExit ) ); //Purpose: Leave the program.
MenuItem miFile = new MenuItem( "&File", new MenuItem[] { miRead, miExit } ); //Complete menu with two entries.
Menu = new System.Windows.Forms.MainMenu( new MenuItem[] { miFile } ); //Attach the menu to Form1.
Text = "Bitmap1"; //Blue title bar.
SetStyle( ControlStyles.ResizeRedraw, true ); //Redirect the OnResize-event to the OnPaint event handler.
Width = 1024; //Initial window size.
Height = 800; //Initial window size. Raise the OnResize-event which calls protected override void OnPaint(...).
try { //Delete this and the following 6 lines if you have no Internet connection running. //try-clause reads an image from the internet.
System.Net.WebRequest webreq = System.Net.WebRequest.Create( "http://www.miszalok.de/Images/Madonna.bmp" ); //Try to reach a bitmap file.
System.Net.WebResponse webres = webreq.GetResponse(); //Wait for response.
System.IO.Stream stream = webres.GetResponseStream(); //Store the response if any.
bmp = (Bitmap)Image.FromStream( stream ); //Convert the response into a bitmap-object.
Invalidate(); //Call protected override void OnPaint(...).
} catch {}; //End of try-clause. If there was no response, forget about the WebRequest. In this case the user has to load an image manually from his own hard disk.
Event Handler private void MenuFileRead( object obj, EventArgs ea )
{ OpenFileDialog dlg = new OpenFileDialog(); //Call the standard modal OpenFileDialog-box.
if ( dlg.ShowDialog() != DialogResult.OK ) return; //Forget it, if there was no reasonable user reaction.
try { bmp = (Bitmap)Image.FromFile( dlg.FileName ); } catch { return; } //Try to read the image using the powerful Bitmap-class. Forget it if that wasn't an image file.
nClicks = 0; //Initialize the mouse-click-counter.
Invalidate(); //Call protected override void OnPaint(...).
Event Handler private void MenuFileExit( object obj, EventArgs ea )
{ Application.Exit(); } //Kill the current instance of program bitmap1.
Event Handler protected override void OnMouseDown( MouseEventArgs e )
{ nClicks++; //Increment the mouse-click-counter.
Invalidate(); //Call protected override void OnPaint(...).
Event Handler protected override void OnPaint( PaintEventArgs e )
{ Graphics g = e. Graphics; //Get a current Graphics-object in order to be able to draw something.
if ( bmp == null ) { g.DrawString( "Open an Image File !", Font, bbrush, 0, 0 ); return; } //Inform the user what to do, if there is no image at all.
Rectangle cr = ClientRectangle; //Store the current size of the client area.
int line = 0; //Vertical position of the first printed line.
switch ( nClicks % 9 ) //Divide the mouse-click-counter by 9 and use the remainder as selector how to react. The modulo operator furnishes cyclic results between 0 and 8 regardless of how many times a mouse button has been pressed.
{ case 0: //Information //The mouse button has been pressed 0, 9, 18 etc. times.
g.DrawString( "RawFormat = " + bmp.RawFormat.ToString(), Font, bbrush, 0, line+=Font.Height ); //Extract the RawFormat-property from class bmp. see msdn2.microsoft.com/en-us/library/system.drawing.image.rawformat.aspx.
if ( bmp.RawFormat.Guid == ImageFormat.Bmp.Guid ) //Extract the Guid-property from the RawFormat-property and compare it with "Bmp.Guid". see http://msdn2.microsoft.com/en-us/library/system.drawing.imaging.imageformat_properties.aspx.
g.DrawString( "BMP", Font, bbrush, 0, line+=Font.Height ); //RawFormat==Bmp.Guid means the Windows-Bitmap Image File Format.
if ( bmp.RawFormat.Guid == ImageFormat.Jpeg.Guid ) //Extract the Guid-property from the RawFormat-property and compare it with "Jpeg.Guid".
g.DrawString( "JPG", Font, bbrush, 0, line+=Font.Height ); //RawFormat==Jpeg.Guid means the JPG Image File Format.
g.DrawString( "Width = " + bmp.Width.ToString() , Font, bbrush, 0, line+=Font.Height ); //Print the no. of columns.
g.DrawString( "Height = " + bmp.Height.ToString() , Font, bbrush, 0, line+=Font.Height ); //Print the no. of rows.
g.DrawString( "PixelFormat = " + bmp.PixelFormat.ToString(), Font, bbrush, 0, line+=Font.Height ); //Print the pixel format and no. of bits per pixel
g.DrawString( "Click on left mouse button !", Font, rbrush, 0, line+=Font.Height); //Advice the user what to do.
break; //End of case 0: .
case 1: //Raw display //The mouse button has been pressed 1, 10, 19 etc. times.
g.DrawImage( bmp, 0, Font.Height ); //Draw the original image in its native size below the existing line of text.
g.DrawString( "Click on left mouse button !", Font, rbrush, 0, 0 ); //
break; //End of case 1: .
case 2: //Center //The mouse button has been pressed 2, 11, 20 etc. times.
Int32 x = (cr.Width - bmp.Width ) / 2; //Left margin.
Int32 y = (cr.Height - bmp.Height) / 2; //Upper margin.
g.DrawImage(bmp, x, y, bmp.Width, bmp.Height); //Center the original image in its native size in the middle of the client area of Form1..
g.DrawString( "Change window size ! Click on left mouse button !", Font, rbrush, 0, 0 ); //Advice the user what to do.
break; //End of case 2: .
case 3: //Horizontal stretch //The mouse button has been pressed 3, 12, 21 etc. times.
x = 0; //Left margin = 0.
y = ( cr.Height - bmp.Height / 2 ) / 2; //Upper margin.
g.DrawImage( bmp, x, y, cr.Width, bmp.Height / 2 ); //full form width, half bmp height //Stretch the image horizontally and squeeze it vertically.
g.DrawString( "Change window size ! Click on left mouse button !", Font, rbrush, 0, 0 ); //Advice the user what to do.
break; //End of case 3: .
case 4: //Vertical stretch //The mouse button has been pressed 4, 13, 22 etc. times.
x = ( cr.Width - bmp.Width / 2 ) / 2; //Left margin.
y = 0; //Upper margin = 0.
g.DrawImage( bmp, x, y, bmp.Width / 2, cr.Height ); //half bmp width, full form height //Squeeze the image horizontally and stretch it vertically.
g.DrawString( "Change window size ! Click on left mouse button !", Font, rbrush, 0, 0 ); //Advice the user what to do.
break; //End of case 4: .
case 5: //Full size //The mouse button has been pressed 5, 14, 23 etc. times.
g.DrawImage( bmp, cr ); //Stretch the image in order to fit exactly into the client area of Form1.
g.DrawString( "Change window size ! Click on left mouse button !", Font, rbrush, 0, 0 ); //Advice the user what to do.
break; //End of case 5: .
case 6: //Mirror //The mouse button has been pressed 6, 15, 24 etc. times.
g.DrawImage( bmp, cr.Width/2, cr.Height/2, cr.Width/2, cr.Height/2 ); //Upright into the lower right quadrant.
g.DrawImage( bmp, cr.Width/2, cr.Height/2, -cr.Width/2, cr.Height/2 ); //Horizontally mirrored into the left lower quadrant.
g.DrawImage( bmp, cr.Width/2, cr.Height/2, cr.Width/2, -cr.Height/2 ); //Vertically mirrored into the right upper quadrant.
g.DrawImage( bmp, cr.Width/2, cr.Height/2, -cr.Width/2, -cr.Height/2 ); //Horiz. and vert. mirrored into the left upper quadrant.
g.DrawString( "Change window size ! Click on left mouse button !", Font, rbrush, 0, 0 ); //Advice the user what to do.
break; //End of case 6: .
case 7: //Zoom animation //The mouse button has been pressed 7, 16, 25 etc. times.
x = cr.Width / 20; //5% of image width.
y = cr.Height / 20; //5% of image height.
for ( Int32 i = 0; i < 20; i++ ) //Draw 20 shrinking images.
g.DrawImage( bmp, 0, 0, cr.Width - x*i, cr.Height - y*i ); //Draw 20 images shrinking from full size to 5%.
g.DrawString( "Change window size ! Click on left mouse button !", Font, rbrush, 0, 0 ); //Advice the user what to do.
break; //End of case 7: .
case 8: //Rotation animation //The mouse button has been pressed 8, 17, 26 etc. times.
Single fx = cr.Width / 100; //Horizontal step width = 1% of image width.
Single fy = cr.Height / 100; //Vertical step height = 1% of image height.
PointF[] p = new PointF[3]; //Triangle with float coordinates p[0].X=p[0].Y=p[1].X=p[1].Y=p[2].X=p[2].Y = 0. This triangle will rotate in 100 steps. p[0] starts as upper left corner (0,0), p[1] starts as upper right corner (cr.Width,0) and p[2] starts as lower left corner (cr.With,cr.Height). Each step shifts p[0] to the right, p[1] to the bottom and p[2] upwards. Thus the three vertices will move along the top, right and left margin of the client area.
p[1].X = cr.Width; //Initialize p[1] to the upper right corner.
p[2].Y = cr.Height; //Initialize p[2] to the lower left corner.
do //The loop starts here.
{ p[0].X += fx; //Shift p[0] to the right.
p[1].Y += fy; //Shift p[1] to the bottom.
p[2].Y -= fy; //Shift p[2] to the top.
g.DrawImage( bmp, p ); //Draw the image that fits to the rotated triangle.
} while ( p[2].Y > 0 ); //Stop the loop when p[2] reaches the top margin of the client area.
g.DrawString( "Change window size ! Click on left mouse button !", Font, rbrush, 0, 0 ); //Advice the user what to do.
break; //End of case 8: .