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Avoid Uncompressing Image Data

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2.3. Memory usage The memory usage of image object is a key factor for a program using image files, because normally a Bitmap object expands image data in memory and the size of memory is usually significant as it is directly related to the dimension of the image. 2.3.1. Avoid uncompressing image data However, the first thing worth to discuss is that the Image.FromStream() has a different approach than other means to load an image file into memory, that makes it is possible to not expand the compressed image data in memory. This can make an enormous difference when the raw size is much larger than the compressed size, such as a JPEG image file of a large dimension with many chunks of same color. The key is using the static method of …show more content…

With this feature, using clone() method is super-fast and it can save significant memory comparing to duplicate with new Bitmap(). However, clone() method will share file lock if the original one was created as new Bitmap(filename), just like to create a new Bitmap object with the constructor. The second method is to use Bitmap(Bitmap) constructor to create a duplicate. The duplicated object has separate memory and does not hold file lock as the original object might have. A test of simple image file shows this method is slower than loading from file directly. 2.4. Capturing a control to a bitmap It is very useful to capture image data of a control or a form into a bitmap object. The key is to use the DrawToBitmap() method of the control or the form. The method is defined in both System.Windows.Forms.Control and System.Windows.Forms.Form, so all subclasses of them have the same function, such as Label, Button, PictureBox, and Dialogs. The following code snippet is a demo of using the method to capture a control into a bitmap. The code to capture a form into a bitmap is almost the same as above. 2.5. Image file types There are multiple image file formats that are supported by Image class. Each supported format is defined as a static property in ImageFormat class in namespace System.Drawing.Imaging (MSDN, n.d.-d).

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