Accepts a column offset to retrieve data from an image and place it in a buffer.
Public Overloads Function GetRowColumn( _
ByVal row As Integer, _
ByVal column As Integer, _
ByVal buffer As IBuffer, _
ByVal bufferIndex As Integer, _
ByVal bufferCount As Integer _
) As Integer
The number of the row to retrieve. The first row is 0, and the last row is 1 less than the image height.
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 to hold the image data that this method gets. The buffer will be filled with uncompressed data.
0-based index into the output buffer. This is the start location of output data.
The number of bytes to retrieve. Consider the bits per pixel, 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 24-bit images, every three bytes represents one pixel. For a 32-bit image, every four bytes represents one pixel. For 48-bit images, every six bytes represents one pixel. For 64-bit images, every eight bytes represents one pixel.
You can use the image 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;
The number of bytes copied.
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 ( bufferCount) in bytes. Therefore, you must consider the bits per pixel of the image when specifying these parameters. The following table describes the rules:
|Bits Per Pixel||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.|
The image memory must be locked when you use this method. Normally, you can call Access to lock the memory before starting an operation that uses this method. Then call Release when the operation is finished.
For more information, refer to Introduction to Image Processing With LEADTOOLS.
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