Displaying Images in Forms

We can include graphics images in a form. There are several formats for graphics images, but this account deals primarily with bitmap images (extension "bmp") which are quite widely used in Windows. A bitmap file is stored in a "lossless" fashion, basically storing a color value for each pixel ("raster" graphics). The actual file format contains various other data as well. A bitmap adapts well to different resolutions but does not necessarily scale well.

Image Class

This is an abstract base class for other classes such as Bitmap.

Properties (some of them)

• Height = height of the image, in pixels.

• Width = width of the image, in pixels.

• Size = width and height of the image, in pixels, as a Size structure. (A Size struct has properties Width and Height.)

Methods (one of them)

     public static Image FromFile(String Filename)

This creates an Image from the file.

There are various other "From" methods to create an Image from other sources.

Bitmap Class

This represents one Image specifically created from a bitmap file.

Constructors (a few of them)

• public Bitmap(Image Original)

• public Bitmap(Image Original, Size S)

  This creates a Bitmap from the Image, scaled to the indicated Size.

• public Bitmap(String Filename)

  This creates a Bitmap from the file.

Properties

We have Width, Height and Size (and more), inherited from Image.

How do we display the image

We will need a Graphics object:

     Graphics G = this.CreateGraphics();

After that, we can use any of several methods. Here are a few:

• DrawImage(Image I, int X, int Y)

  This draws image I at the location (X, Y).

• DrawImage(Image I, Point P)

  This is similar but the (X, Y) data is in a Point.

• DrawImage(Image I, int X, int Y, int Width, image Height)

  This draws image I at (X, Y) with the given dimensions.

TextureBrush Class

The TextureBrush class is derived from the Brush class and is used for "tiling".

Sometimes we want to use an image as a background, filling a space with copies of the image side by side. This is called tiling.

Constructors (a couple of them)

• TextureBrush(Image I)

  This creates new TextureBrush that uses the indicated image).

• TextureBrush(Image I, WrapMode W)

  This creates a new TextureBrush that uses the specified image and wrap mode.

Here WrapMode indicates a member of the WrapMode enumerated type, which includes values such as:

• Tile
• TileFlipX -- the image is flipped horizontally between uses
• TileFlipY -- the image is flipped vertically between uses
• TileFlipXY -- the image is flipped both ways between uses

Examples

     // This draws the image at the given location.
     Graphics G = this.CreateGraphics();
     Bitmap B = new Bitmap("A_Picture.bmp");
     DrawImage(B, 100, 100);

     // This fills a rectangle with copies of the image.
     Graphics G = this.CreateGraphics();
     Bitmap B = new Bitmap("A_Picture.bmp");
     TextureBrush TB = new TextureBrush(B, WrapMode.Tile);
     Rectangle R = new Rectangle(20, 20, 500, 500);
     G.FillRectangle(TB, R);

     // This fills a rectangle with copies of the image with
     // horizontal flipping.
     Graphics G = this.CreateGraphics();
     Bitmap B = new Bitmap("A_Picture.bmp");
     TextureBrush TB = new TextureBrush(B, WrapMode.TileFlipX);
     Rectangle R = new Rectangle(20, 20, 500, 500);
     G.FillRectangle(TB, R);

PictureBox class

The PictureBox is used to display an image from a file such as bitmap, JPEG, GIF, pNG or some others.

PictureClass has various properties, such as:

• Image Image -- the image to be displayed
• Color BackColor -- background color for the PictureBox (in case the image does not fill all of it)
• BorderStyle BorderStyle -- border style for the PictureBox; here BorderStyle is an enumeration (single-line, 3-D, or none)
• Size Size -- size of the PictureBox; here Size is the Size struct which has properties such as Height and Width
• PictureBoxSize Mode SizeMode -- indicates how the image is displayed; here PictureBoxSizeMode is an enumeration, and an image may be centered, clipped if necessary, enlarged, shrunk, etc.

Example (adapted from a MSDN page):

private Bitmap MyImage;

public void ShowMyImage(String fileToDisplay, int xSize, int ySize)
{
   // Stretches the image to fit the pictureBox.
   pictureBox1.SizeMode = PictureBoxSizeMode.StretchImage;
   MyImage = new Bitmap(fileToDisplay);
   pictureBox1.ClientSize = new Size(xSize, ySize);
   pictureBox1.Image = (Image) MyImage;
}