Image

With this type in the C# language and .NET, you can act upon an abstraction of all those image types. Images are complex and there are many image formats.

Constructor

There is no constructor for the Image type. Instead, look into using the Image.FromFile or Image.FromStream methods. These will return a new instances of the Image type.

FromFile

The FromFile method is the easiest way to get an instance of a new Image in memory. Internally, FromFile uses functions from the GDI+ libraries of Microsoft Windows.

using System;
using System.Drawing;

class Program
{
    static void Main()
    {
        string[] array =
        {
            @"C:\thumbnail.png",
            @"C:\Users\Sam2\bluearrow1.png"
        };

        foreach (string fileName in array)
        {
            Image image = Image.FromFile(fileName);
            int width = image.Width;
            int height = image.Height;

            Console.WriteLine("{0}: {1} {2}", fileName, width, height);
        }
    }
}
C:\thumbnail.png: 9 40
C:\Users\Sam2\bluearrow1.png: 208 208

Image.FromStream

The Image.FromStream method works the same as the FromFile method but acts upon a Stream instance to get the image data.

using System;
using System.Drawing;
using System.IO;

class Program
{
    static void Main()
    {
        using (FileStream stream = File.Open("C:\\t4\\2Z", FileMode.Open))
        using (Image image = Image.FromStream(stream))
        {
            Console.WriteLine(image.Size);
        }
    }
}
{Width=280, Height=248}

Tag

We can assign any object reference to the Tag property. The Tag here is much like the Tag property in Windows Forms—we can attach a reference of any type in memory.

using System;
using System.Drawing;

class Program
{
    static void Main()
    {
        using (Image image = Image.FromFile("C:\\t4\\2Z"))
        {
            image.Tag = "Dot Net Perls image";
            // Do stuff.
            Console.WriteLine(image.Tag);
        }
    }
}
Dot Net Perls image

Resolution

Most bitmap images, such as PNG files and JPG files, will have a HorizontalResolution and VerticalResolution of 72 each.

using System;
using System.Drawing;

class Program
{
    static void Main()
    {
        Image i = Image.FromFile("C:\\t4\\2Z");
        float h = i.HorizontalResolution;
        float v = i.VerticalResolution;
        Console.WriteLine("{0}, {1}", h, v);
    }
}
72, 72

RotateFlip

If you need to rotate or flip an image, the RotateFlip method is just what you need. The method allows you to both rotate and flip in a single method call.

using System;
using System.Drawing;

class Program
{
    const string _input = "C:\\t4\\2Z";

    static void Main()
    {
        M(RotateFlipType.Rotate180FlipNone);
        M(RotateFlipType.Rotate180FlipX);
        M(RotateFlipType.Rotate180FlipXY);
        M(RotateFlipType.Rotate180FlipY);
        M(RotateFlipType.Rotate270FlipNone);
        M(RotateFlipType.Rotate270FlipX);
        M(RotateFlipType.Rotate270FlipXY);
        M(RotateFlipType.Rotate270FlipY);
        M(RotateFlipType.Rotate90FlipNone);
        M(RotateFlipType.Rotate90FlipX);
        M(RotateFlipType.Rotate90FlipXY);
        M(RotateFlipType.Rotate90FlipY);
        M(RotateFlipType.RotateNoneFlipNone);
        M(RotateFlipType.RotateNoneFlipX);
        M(RotateFlipType.RotateNoneFlipXY);
        M(RotateFlipType.RotateNoneFlipY);
    }

    static void M(RotateFlipType type)
    {
        Image i = Image.FromFile(_input);
        i.RotateFlip(type);
        i.Save("C:\\" + type.ToString() + ".png");
    }
}

Height, Width

The Height and Width properties can be used to generate HTML files that contain the height and width attributes for an image that is on the disk.

using System;
using System.Drawing;

class Program
{
    static void Main()
    {
        Image image = Image.FromFile("C:\\background1.png", false);
        Console.WriteLine(image.Width);
        Console.WriteLine(image.Height);
        Console.WriteLine(image.PhysicalDimension);
    }
}
180
110
{Width=180, Height=110}

GetThumbnailImage

To save bandwidth, websites often use thumbnail images that users can click on to see larger versions. GetThumbnailImage() can generate these images.

Dispose

Because the Image type implements IDisposable, it can be used with the using statement in a resource acquisition block. This can reduce resource usage.

Image formats

Obviously, not all image formats are supported by the Image type. The PNG type is supported. More exotic types such as Photoshop image formats would not be supported.

Save

After providing a target file name, the Save method will write the image data in memory to the location. This is useful after rotating or resizing an image.

Summary

We explored many different aspects of the Image type in C#. With abstraction, the Image type allows us to use image formats in a simple way, but with limitations.