Browse Prior Art Database

Left Clip Right Clip using Hardware Clipping

IP.com Disclosure Number: IPCOM000115130D
Original Publication Date: 1995-Mar-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 4 page(s) / 78K

Publishing Venue

IBM

Related People

Lawless, WF: AUTHOR

Abstract

Images are often stored in system memory and moved into a graphics Frame Buffer via some sort of DMA to be displayed on the monitor. These images or pictures are stored in what is called a pixmap in system memory and the process of moving the image from system memory to the Frame Buffer is called a Bit BLT or Bit Block Transfer. Now if these images are loaded into system memory starting and ending on even word address boundaried then the data is ready for DMA and the data can be moved into the Frame Buffer and the picture will appear on your display. However, more often then not images will start and stop on what ever address they were loaded into and based on how much of the picture you want to see. Most hardware DMA capability can only move data on even word boundaried thus sending more pixels for display then are wanted.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 53% of the total text.

Left Clip Right Clip using Hardware Clipping

      Images are often stored in system memory and moved into a
graphics Frame Buffer via some sort of DMA to be displayed on the
monitor.  These images or pictures are stored in what is called a
pixmap in system memory and the process of moving the image from
system memory to the Frame Buffer is called a Bit BLT or Bit Block
Transfer.  Now if these images are loaded into system memory starting
and ending on even word address boundaried then the data is ready for
DMA and the data can be moved into the Frame Buffer and the picture
will appear on your display.  However, more often then not images
will start and stop on what ever address they were loaded into and
based on how much of the picture you want to see.  Most hardware DMA
capability can only move data on even word boundaried thus sending
more pixels for display then are wanted.

      This disclosure will show a method of clipping of the unwanted
pixels in hardware and displaying only the exact picture wanted.
Thus the name Left Clip Right Clip will clip the unwanted pixels from
the left and right sides of the BLT rectangle.

      Left Clip Right Clip Register - The following register is
needed in the hardware design.  This register is written by the
system software with the desired value to be clipped off the front
and back during the Bit BLT operation.

      Register  Description - This register specifies the Number of
Pixels clipped off from the f...