Methods and systems for improving display resolution in images using sub-pixel sampling and visual error filtering

• US 6,608,632 B2
• Filed: 12/12/2000
• Issued: 08/19/2003
• Est. Priority Date: 06/12/2000
• Status: Expired due to Fees

• Current Assignee: Sharp Laboratories of America Incorporated (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Laboratories of America Incorporated (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Daly, Scott J., Kovvuri, Rajesh Reddy K.
• Primary Examiner(s): Shalwala, Bipin
• Assistant Examiner(s): Osorio, Ricardo
• Application Number:
  US09/735,424
• Publication Number:
  US 20020093521A1
• Time in Patent Office: 980 Days
• Field of Search: 345/698, 345/699, 345/603, 345/604, 345/611, 345/613, 345/616, 345/3.3, 345/3.4, 348/450, 382/275, 382/274, 382/254, 382/263, 382/264, 382/299
• US Class Current: 345/698
• CPC Class Codes: G09G 2340/0457 Improvement of perceived resolution by subpixel rendering
• CPC Class Codes: G09G 3/2003 Display of colours specific for liquid crystal displays G09G3/3607

Abstract

Embodiments of the present invention provide systems and methods for converting a higher-resolution image to a lower-resolution image with reduced visible errors. These embodiments comprise splitting a higher-resolution opponent color domain (OCD) image into separate initial luminance and initial chrominance channels followed by sub-pixel sampling on said initial luminance channel thereby creating an additive color domain (ACD) luminance image. This ACD luminance image is then converted into an OCD luminance image and split into separate sub-pixel sampled (SPS) luminance and SPS chrominance channels. The SPS chrominance channels are high-pass filtered and the initial chrominance channels are low-pass filtered. The filtered initial chrominance channels are sub-sampled and combined with the high-pass filtered SPS chrominance channels. These combined chrominance channels are then combined with said SPS luminance channel to form an error-reduced lower-resolution image.

Claims

1. A method for converting a higher-resolution image to a lower-resolution image with reduced visible errors, said method comprising the acts of:

splitting a higher-resolution opponent color domain (OCD) image into separate initial luminance and initial chrominance channels;

performing sub-pixel sampling on said initial luminance channel thereby creating an additive color domain (ACD) luminance image;

converting said ACD luminance image into an OCD luminance image;

splitting said OCD luminance image into separate sub-pixel sampled (SPS) luminance and SPS chrominance channels;

high-pass filtering said SPS chrominance channels;

low-pass filtering said initial chrominance channels;

sub-sampling said filtered initial chrominance channels;

combining said sub-sampled, low-pass filtered chrominance channels with said high-pass filtered SPS chrominance channels; and

combining said combined chrominance channels with said SPS luminance channel to form an error-reduced lower-resolution image.

2. The method of claim 1 wherein said higher-resolution image is an additive color domain image which is converted to an opponent color domain image prior to said splitting a higher-resolution OCD image.

3. The method of claim 1 wherein said additive color domain image is an RGB image.

4. The method of claim 1 wherein said opponent color domain images are YCrCb images.

5. The method of claim 1 wherein said opponent color domain images are LAB images.

6. The method of claim 1 wherein said high-pass filtering comprises unsharp-mask filtering.

7. The method of claim 1 wherein said high-pass filtering comprises the acts of:

filtering said SPS chrominance channels via an unsharp-mask filter with a Gaussian low-pass kernel resulting in low-pass SPS chrominance channels; and

subtracting said SPS low-pass chrominance channels from said SPS chrominance channels to yield high-pass filtered SPS chrominance channels.

8. The method of claim 1 wherein said chrominance channels comprise a red-green channel and a blue-yellow channel.

9. The method of claim 1 wherein said chrominance channels comprise the Cr and Cb channels of a YCrCb image.

10. The method of claim 1 wherein said chrominance channels comprise the “

a” and

“

b”

channels of a CIELab image.

11. The method of claim 1 further comprising the act of transforming said error-reduced lower-resolution image to an RGB image.

12. The method of claim 1 wherein said act of performing sub-pixel sampling comprises converting said initial luminance channel into an additive color domain (ACD) luminance image and sampling said ACD luminance image.

13. A method for displaying a higher-resolution image at a lower-resolution with reduced visible errors, said method comprising the acts of:

converting a higher-resolution RGB image to a higher-resolution opponent color domain (OCD) image;

splitting said higher-resolution OCD image into separate initial luminance and initial chrominance channels;

converting said initial luminance channel into a RGB luminance image;

performing sub-pixel sampling on said RGB luminance image;

converting said sub-pixel sampled (SPS) RGB luminance image into a SPS OCD luminance image;

splitting said SPS-OCD luminance image into separate SPS luminance and SPS chrominance channels;

high-pass filtering said SPS chrominance channels;

low-pass filtering said initial chrominance channels of said higher-resolution OCD image;

sub-sampling said filtered initial chrominance channels;

combining said sub-sampled, low-pass filtered chrominance channels with said high-pass filtered SPS chrominance channels; and

combining said combined chrominance channels with said SPS luminance channel to form an error-reduced OCD lower-resolution image; and

converting said error-reduced OCD lower-resolution image to an error-reduced lower-resolution RGB image.

14. A method for converting a higher-resolution image to a lower-resolution image with reduced visible errors, said method comprising steps for:

splitting a higher-resolution opponent color domain (OCD) image into separate initial luminance and initial chrominance channels;

performing sub-pixel sampling on said initial luminance channel thereby creating an additive color domain (ACD) luminance image;

converting said ACD luminance image into an OCD luminance image;

splitting said OCD luminance image into separate sub-pixel sampled (SPS) luminance and SPS chrominance channels;

high-pass filtering said SPS chrominance channels;

low-pass filtering said initial chrominance channels;

sub-sampling said filtered initial chrominance channels;

combining said sub-sampled, low-pass filtered chrominance channels with said high-pass filtered SPS chrominance channels; and

combining said combined chrominance channels with said SPS luminance channel to form an error-reduced lower-resolution image.

15. A system for converting a higher-resolution image to a lower-resolution image with reduced visible errors, said system comprising:

a first splitter for splitting a higher-resolution opponent color domain (OCD) image into separate initial luminance and initial chrominance channels;

a sub-pixel sampler for performing sub-pixel sampling on said initial luminance channel thereby creating an additive color domain (ACD) luminance image;

a converter for converting said ACD luminance image into an OCD luminance image;

a second splitter for splitting said OCD luminance image into separate sub-pixel sampled (SPS) luminance and SPS chrominance channels;

a high-pass filter for high-pass filtering said SPS chrominance channels;

a low-pass filter for low-pass filtering said initial chrominance channels;

a sub-sampler for sub-sampling said filtered initial chrominance channels;

a first combiner for combining said sub-sampled, low-pass filtered chrominance channels with said high-pass filtered SPS chrominance channels; and

a second combiner for combining said combined chrominance channels with said SPS luminance channel to form an error-reduced lower-resolution image.

16. A computer readable medium comprising instructions for converting a higher-resolution image to a lower-resolution image with reduced errors, said instructions comprising the acts of:

splitting a higher-resolution opponent color domain (OCD) image into separate initial luminance and initial chrominance channels;

performing sub-pixel sampling on said initial luminance channel thereby creating an additive color domain (ACD) luminance image;

converting said ACD luminance image into an OCD luminance image;

splitting said OCD luminance image into separate sub-pixel sampled (SPS) luminance and SPS chrominance channels;

high-pass filtering said SPS chrominance channels;

low-pass filtering said initial chrominance channels;

sub-sampling said filtered initial chrominance channels;

combining said sub-sampled, low-pass filtered chrominance channels with said high-pass filtered SPS chrominance channels; and

combining said combined chrominance channels with said SPS luminance channel to form an error-reduced lower-resolution image.

17. A computer data signal embodied in an electronic transmission, said signal having the function of converting a higher-resolution image to a lower-resolution image with reduced visible errors, said signal comprising instructions for:

splitting a higher-resolution opponent color domain (OCD) image into separate initial luminance and initial chrominance channels;

performing sub-pixel sampling on said initial luminance channel thereby creating an additive color domain (ACD) luminance image;

converting said ACD luminance image into an OCD luminance image;

splitting said OCD luminance image into separate sub-pixel sampled (SPS) luminance and SPS chrominance channels;

high-pass filtering said SPS chrominance channels;

low-pass filtering said initial chrominance channels;

sub-sampling said filtered initial chrominance channels;

combining said sub-sampled, low-pass filtered chrominance channels with said high-pass filtered SPS chrominance channels; and

combining said combined chrominance channels with said SPS luminance channel to form an error-reduced lower-resolution image.