Image analysis – Image transformation or preprocessing – Changing the image coordinates
Reexamination Certificate
1999-12-27
2004-04-20
Chen, Wenpeng (Department: 2624)
Image analysis
Image transformation or preprocessing
Changing the image coordinates
C345S660000, C348S581000
Reexamination Certificate
active
06724948
ABSTRACT:
BACKGROUND
This invention relates to scaling images for display.
In video images, the number of pixels in an image determines the quality, or resolution, of the image. More pixels in an image translates to higher resolution.
High definition television (HDTV) images, for example, have a high resolution (e.g., 1920×540 1080
i
(interlaced)) that cannot be directly displayed on a typical personal computer (PC) monitor without scaling the images to a lower resolution (e.g., 1280×720). Additionally, the images typically occupy a small section of the PC monitor, requiring further scaling to a lower resolution (e.g., 480×135).
One way to scale HDTV images to a usable size for PC monitors is by overlay scaling. Overlay scaling reads an HDTV image from the computer's memory and scales it horizontally and vertically. Overlay scales images “on the fly,” while the PC monitor is being refreshed. The scaled image replaces (“overlays”) the previously scaled image being displayed on the PC monitor. The number of images scaled and displayed per second, e.g., 85 frames per second (85 Hz), enables a computer user to view a continuous video picture sequence on the monitor.
For example, in
FIG. 1
, overlay scaling reads a 1920×540 1080
i
HDTV image
12
from a PC's memory, creates a 4:1 downscaled 480×135 image
14
, and displays the image
14
on the PC's monitor. As seen in
FIG. 2
, image
12
is one of a sequence of incoming video images that appear at an image update rate of 60 frames per second (60 Hz) and are stored temporarily in memory
13
. Because image
12
is interlaced only every other line of the image is displayed), the “real” update rate is 30 frames per second (30 Hz). The overlay process reads successive images
12
from computer memory
13
at a PC CRT (cathode-ray tube) refresh rate, e.g., 85 frames per second (85 Hz), downscales them, and delivers them to the monitor for display.
Also referring to
FIG. 3
, to create the 4:1 downscaled image
14
, an overlay process reads sixteen pixels of image
12
(one pixel segment
16
), compresses them to form one pixel of image
14
, displays the one pixel, and proceeds to the next segment
16
. The segments
16
are processed from left to right in each row, working from the top row to the bottom row. This overlay scaling requires an average memory bandwidth of 176 MB/sec, where memory bandwidth equals (horizontal resolution, 1920)×(vertical resolution, 540)×(refresh rate, 85)×(bytes per pixel, 2), and a peak memory bandwidth of 1054 MB/sec (1920×540×85×12). Some PC memory systems cannot supply such a high bandwidth, so the PC compensates by dropping lines of the image. For example, dropping every other line would reduce the bandwidth requirements by 50%. Dropping lines, however, decreases image quality because the information in every pixel should contribute to the downscaled image.
SUMMARY
In general, in one aspect, the invention features scaling a graphic image that has pixels arranged in rows and columns by processing a succession of segments. Each segment comprises contiguous pixels. The row and column dimensions of each segment do not correspond to an intended degree of scaling in both dimensions. The processing of each segment produces an intermediate pixel. The intermediate pixels form a stream. The intermediate stream of pixels is processed to form a final two-dimensional scaled image.
In another aspect, the invention features scaling each image that appears in a video sequence of images for display on a display device that displays downscaled images by compressing each image in a first scaling process to form a sequence of intermediate, partially scaled images, and compressing each of the intermediate images in a second scaling process to form a final sequence of scaled images.
Other advantages and features will become apparent from the following description and from the claims.
REFERENCES:
patent: 5764807 (1998-06-01), Pearlman et al.
patent: 5831592 (1998-11-01), Cahill, III
patent: 6144412 (2000-11-01), Hirano et al.
patent: 6327000 (2001-12-01), Auld et al.
LandOfFree
Scaling images for display does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Scaling images for display, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Scaling images for display will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3208330