Browse Prior Art Database

Pixel Mapping Method for Writing Rectangles and Horizontal/Vertical Lines

IP.com Disclosure Number: IPCOM000104592D
Original Publication Date: 1993-May-01
Included in the Prior Art Database: 2005-Mar-19
Document File: 4 page(s) / 91K

Publishing Venue

IBM

Related People

Aoki, Y: AUTHOR [+2]

Abstract

Disclosed is a method for the storage organization of the frame buffer. With this article, a flexible memory access window of the frame buffer is realized. It provides pixel addressability in both horizontal-span, vertical-span and a square block of pixels on the screen. This flexible memory access window is very useful for line drawing.

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Pixel Mapping Method for Writing Rectangles and Horizontal/Vertical Lines

      Disclosed is a method for the storage organization of the frame
buffer.  With this article, a flexible memory access window of the
frame buffer is realized.  It provides pixel addressability in both
horizontal-span, vertical-span and a square block of pixels on the
screen.  This flexible memory access window is very useful for line
drawing.

      To explain the method, a small model screen of 8x4 pixels is
introduced as shown in Fig. 1.  And the method is discussed on
4-banks of memory chips in the frame buffer configuration.

      A typical implementation for the model screen of Fig. 1 with 4
memory banks is to map the pixels along with the horizontal scanline.
That is, a pixel which corresponds to the screen coordinate (j,i) is
stored into the k-th bank of memory (0 <= k<= n) so that it satisfies
k = j/4.

      A common problem of this type of mapping can be observed when a
inclined line is to draw.  While a 4 pixel length of horizontal line
starting with coordinate (0,0) can be written into the memories with
one cycle, another 4 pixel length of line from the coordinate (0,0)
to (3,3) needs 4 cycles to update the memories.

      Several approaches have been proposed for this problem.  Some
approaches provide a solution to access the frame buffer memories in
both horizontally and vertically.  Others provide a solution to
access in both horizontal-span and rectangles.  Fig. 2 is a block
diagram schematically illustrating one embodiment of a pixel mapping
method of the past invention in accordance with the model screen of
Fig. 1.  This conventional methodology supports 2 x 2 or 1
(horizontal) x 4 access window but not 4 (horizontal) x 1.

   ...