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Thumbnails Generation

, 6 Mar 2009 CPOL 44.1K 2.7K 58
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A generic way for generating thumbnails

Introduction

I started as a developer several years ago creating websites. Now I'm working for a company which creates websites, but also multimedia applications. Each time we start developing a new solution, there's this need for image processing. In case of a website we need to generate thumbnails, and for our Windows applications images are restricted to a certain size. To accomplish thumbnails creation and image resizing, we use standard .NET Framework functions. However I was sick and tired of developing the same code over and over again with a slight difference required for each solution. Therefore I decided to develop an image processing class which is able to process images in a more dynamic way. 

Background

Basically the class is pretty simple. It resizes images and stores them again (or returns the image as an object if you like). Depending on your needs, you're able to set the image's size, quality, resizing method and so forth.

Using the Code

The ThumbnailCreationclass exposes four properties:

  • ScalingOption
  • MaxImageLength
  • FileFormat
  • Quality

ScalingOption (read-only) Property

The scaling option enables you to tell the ThumbnailCreationclass to scale the image in different ways. There are three options available:

  • MaintainAspect
  • CenterImage
  • FixedSize

You need to set the ScalingOptionusing a method called SetScalingOption(), which forces you to also define a size when scaling option FixedSizeis used.
The default is called MaintainAspectwhich will maintain the aspect ratio and resize the image so that the largest image side (width or height) equals the value set using the MaxImageLengthproperty.

MaintainAspect.jpg

When the ScalingOptionis set to CenterImage, the center of the image will be scaled so that the largest side (width of height) of the image equals the value set using the MaxImageLengthproperty. The center of the image is a square of half the width and half the height of an image. The image below shows you the result of a thumbnail created using the CenterImagescaling option.

CenterImage.jpg

The third scaling option is FixedSize. You need to define a size and your source image will be scaled to that size.

MaxImageLength Property

The MaxImageLengthproperty is used to define the size of thumbnails. This property is only used for the scaling options MaintainAspectand CenterImage. The largest side of the image (width or height) will equal this value in pixels. The remaining side is scaled so that the aspect ratio of the image will be maintained.

FileFormat Property

The FileFormatproperty enables you to define whether images will be stored as JPEG or PNG image. The default is JPEG. This option is added because you may want to use the PNG format for transparency.

Examples

And now... a few examples of calling the object's StoreThumbnail(which actually stores a thumbnail version of your image on the harddrive). The next example shows you the easiest way of generating a thumbnail accepting all default values.

using (ThumbnailCreation objThumbnailCreator = new ThumbnailCreation())
    objThumbnailCreator.StoreThumbnail(SourceFile, DestinationFile);

The example below shows the code for generating a thumbnail having the ScalingOptionproperty set to CenterImage. The default thumbnail size of 120 pixels is changed to 150 pixels and the image's format will be PNG.

using (ThumbnailCreation objThumbnailCreator = new ThumbnailCreation())
{
    objThumbnailCreator.MaxImageLength = 150; // Max image side to 150 pixels
    objThumbnailCreator.Quality = 100; 	// Best quality
    objThumbnailCreator.SetScalingOption(ScalingOptions.CenterImage);
    objThumbnailCreator.FileFormat = FileFormats.PNG;
    objThumbnailCreator.StoreThumbnail(SourceFile, DestinationFile);
}

History

  • 2009/03/06 - Initial version

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

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About the Author

Eduard Keilholz
Software Developer (Senior) http://www.today-it.nl
Netherlands Netherlands
In 1998 I started as webdesigner programming websites in Perl and later PHP. After two years wrote most of the websites in ASP and from then on lost the feeling with a linux/unix platform.

Since 2001 interested in Windows applications and now writing software using mostly C# for about 7 years now.

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Comments and Discussions

 
GeneralDetermineSizeByRatio Pin
lGiles19-May-09 10:34
memberlGiles19-May-09 10:34 
GeneralRe: DetermineSizeByRatio Pin
Eduard Keilholz19-May-09 21:28
memberEduard Keilholz19-May-09 21:28 
GeneralRe: DetermineSizeByRatio Pin
lGiles20-May-09 5:47
memberlGiles20-May-09 5:47 
GeneralRe: DetermineSizeByRatio Pin
Eduard Keilholz20-May-09 10:54
memberEduard Keilholz20-May-09 10:54 
GeneralRe: DetermineSizeByRatio Pin
lGiles20-May-09 11:04
memberlGiles20-May-09 11:04 
GeneralRe: DetermineSizeByRatio Pin
Eduard Keilholz25-May-09 21:15
memberEduard Keilholz25-May-09 21:15 
GeneralRe: DetermineSizeByRatio Pin
lGiles26-May-09 8:09
memberlGiles26-May-09 8:09 
GeneralRe: DetermineSizeByRatio Pin
Eduard Keilholz26-May-09 23:55
memberEduard Keilholz26-May-09 23:55 

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