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LoadAsync(Stream,Int32,Int32,Int32,RasterSizeFlags,CodecsLoadByteOrder,Object) Method

Summary

Loads an image file asynchronously to the desired width, height, and bits per pixel, resizing the image as it loads.

Syntax

C#
VB
Java
C++
public RasterImage LoadAsync(  
   Stream stream, 
   int width, 
   int height, 
   int bitsPerPixel, 
   RasterSizeFlags flags, 
   CodecsLoadByteOrder order, 
   object userState 
) 

Public Overloads Function LoadAsync( _ 
   ByVal stream As Stream, _ 
   ByVal width As Integer, _ 
   ByVal height As Integer, _ 
   ByVal bitsPerPixel As Integer, _ 
   ByVal flags As RasterSizeFlags, _ 
   ByVal order As CodecsLoadByteOrder, _ 
   ByVal userState As Object _ 
) As RasterImage 

public Object loadAsync(ILeadStream stream, int width, int height, int bitsPerPixel, RasterSizeFlags flags, CodecsLoadByteOrder order, Object userState) 

public: 
RasterImage^ LoadAsync(  
   Stream^ stream, 
   int width, 
   int height, 
   int bitsPerPixel, 
   RasterSizeFlags flags, 
   CodecsLoadByteOrder order, 
   Object^ userState 
)  

Parameters

stream
A Stream containing the image data to load.

width
New width of the image in pixels.

height
New height of the image in pixels.

bitsPerPixel
Resulting image pixel depth. Valid values are:

Value Meaning
0 Keep the original file's pixel depth (Do not convert).
1 to 8 The specified bits per pixel in the resulting image.
12 12 bits per pixel in the resulting image.
16 16 bits per pixel in the resulting image.
24 24 bits per pixel in the resulting image.
32 32 bits per pixel in the resulting image.
48 48 bits per pixel in the resulting image.
64 64 bits per pixel in the resulting image.

flags
Flag that indicates the type of resizing to use. Possible values are:

Value Meaning
RasterSizeFlagsRasterSizeFlags.None Normal resizing
RasterSizeFlagsRasterSizeFlags.Resample Linear interpolation resizing
RasterSizeFlagsRasterSizeFlags.Bicubic Bicubic interpolation resizing
RasterSizeFlagsRasterSizeFlags.FavorBlack Not supported

order
Color order for 16-bit, 24-bit, 32-bit, 48-bit, and 64-bit images. If the resulting image is less than 16 bits per pixel, this will have no effect since palletized images have no order. The following are valid values.

Value Meaning
CodecsLoadByteOrder.Rgb Red, green, and blue color order in memory
CodecsLoadByteOrder.Bgr Blue, green, and red color order in memory
CodecsLoadByteOrder.Gray 12 or 16-bit grayscale image. 12 and 16-bit grayscale images are only supported in the Document/Medical Imaging editions.
CodecsLoadByteOrder.RgbOrGray Load the image as red, green, blue OR as a 12 or 16-bit grayscale image. 12 and 16-bit grayscale images are supported in the Document/Medical Imaging editions
CodecsLoadByteOrder.BgrOrGray Load the image as blue, green, red OR as a 12 or 16-bit grayscale image. 12 and 16-bit grayscale images are supported in the Document/Medical Imaging editions
CodecsLoadByteOrder.Romm ROMM order. ROMM only supports 24 and 48-bit images
CodecsLoadByteOrder.BgrOrGrayOrRomm Load the image as blue, green, red OR as a 12 or 16-bit grayscale image OR as ROMM. 12 and 16-bit grayscale images are supported in the Document/Medical Imaging editions only. ROMM only supports 24 and 48-bit color images.

userState
A user-defined object that is passed to the method invoked when the asynchronous operation completes.

Return Value

The RasterImage object that this method loads.

Remarks

This method resizes a file to the desired width, height, and bits per pixel as it loads. Note that the original file is not completely loaded into memory. This method is ideal for sampling large images (i.e. generating a thumbnail) without the memory overhead of loading the large file itself.

The file can be in any supported image file format and bits per pixel, whether compressed or uncompressed.

LEADTOOLS will attempt to load corrupted files so you can see at least a portion of the image. For these images, the load methods succeed, but LoadStatus will return an error code.

Use the CodecsLoadOptions class to set up other load option parameters before calling this method.

Support for 12 and 16-bit grayscale, and 48 and 64-bit color images is only available in the Document/Medical Imaging editions.

For supported formats, refer to Summary of All Supported Image File Formats.

LEADTOOLS loads all PDF files as Raster PDF uncompressed RasterImageFormat.RasPdf, regardless of the compression and color space used when saving the file.

The RasterCodecs class supports loading image files asynchronously using the LoadAsync methods. When calling any of these methods, the caller thread will not be blocked and the method will return instantly with an instance of RasterImage that is in a loading status (RasterImage.IsLoading set to true). You should not use the other properties of this object while the object is in loading status.

When the RasterCodecs object finishes loading the image, the various properties of the RasterImage will be populated with the image information and data and the RasterImage.IsLoading property will be set to false.

Do not poll the RasterImage.IsLoading property to determine whether the image has finished loading. Instead, subscribe to the LoadAsyncCompleted event to get notification when the LoadAsync operation has completed and whether any errors occurred.

The LoadAsyncCompleted event data will also contain the same object returned from LoadAsync so you do not have to keep the original object in your application.

The CodecsLoadOptions.AllPages property controls whether RasterCodecs will try to load all pages or just the first page if the image data contains multiple pages.

Requirements

Target Platforms

Help Version 20.0.2018.6.21
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