ResizeBuffer(int,int,IntPtr,long) Method

Summary

Retrieves resized data in an unmanaged buffer, one line at a time.

Syntax

C++

public void ResizeBuffer( 
   int row, 
   int column, 
   IntPtr buffer, 
   long bytes 
)

Public Overloads Sub ResizeBuffer( _ 
   ByVal row As Integer, _ 
   ByVal column As Integer, _ 
   ByVal buffer As IntPtr, _ 
   ByVal bytes As Long _ 
)

public: 
void ResizeBuffer(  
   int row, 
   int column, 
   IntPtr buffer, 
   int64 bytes 
)

Parameters

row
The number of the row to retrieve. The first row is 0, and the last row is 1 less than the image Height.

column
The column offset within the row to retrieve. The first column offset is 0, and the last column offset is 1 less than the image Width.

buffer
The unmanaged buffer to hold the image data that this method gets.

bytes
The number of bytes to retrieve. Consider the BitsPerPixel, and avoid specifying a number that goes past the end of the row.

For a 1-bit image, each byte represents 8 pixels.
For a 4-bit image, each byte represents 2 pixels.
For an 8-bit image, each byte represents 1 pixel.
For a 16-bit image, every 2 bytes represents one pixel.
For a 24-bit image, every three bytes represents one pixel.
For a 32-bit image, every four bytes represents one pixel.
For a 48-bit image, every six bytes represents one pixel.
For a 64-bit image, every eight bytes represents one pixel.

You can use the BitsPerPixel property with integer math to calculate the number of bytes needed for a particular number of pixels. For example:

NumberOfBytes = Image.BitsPerPixel * (Image.Width * Image.Height + 7) / 8;

Remarks

By using this low-level method to get any part of a row, you can write a procedure that accesses a single pixel or a rectangular area within the image.

This method accepts an offset parameter ( column) in pixels and a length ( bytes) in bytes. Therefore, you must consider the BitsPerPixel of the image when specifying these parameters. The following table describes the rules:

BitsPerPixel	Column Offset (in Pixels)	Bytes to Get
1	Must be a multiple of 8 (such as 0,8, or 16).	Can be any number up to the end of the row. Consider that there are 8 pixels per byte.
4	Must be an even number (such as 0, 2, or 4).	Can be any number up to the end of the row. Consider that there are 2 pixels per byte.
8	Can be any column within the image.	Can be any number up to the end of the row. Consider that there is 1 pixel per byte.
16	Can be any column within the image.	Must be a multiple of 2 (such as 2, 4, or 6), because there are 2 bytes per pixel.
24	Can be any column within the image.	Must be a multiple of 3 (such as 3, 6, or 9), because there are 3 bytes per pixel.
32	Can be any column within the image.	Must be a multiple of 4 (such as 4, 8, or 12), because there are 4 bytes per pixel.
48	Can be any column within the image.	Must be a multiple of 6 (such as 6, 12, or 18), because there are 6 bytes per pixel.
64	Can be any column within the image.	Must be a multiple of 8 (such as 8, 16, or 24), because there are 8 bytes per pixel.

Do not pass a value in bytes that goes past the end of the row. The process is faster when rows are retrieved sequentially, either top-down or bottom-up.

For more information, refer to Introduction to Image Processing With LEADTOOLS.

Example

Refer to RasterImageResize.

Requirements

Target Platforms