LUMINANCE-BIASED SHARPENING FOR THERMAL MEDIA PRINTING

• US 20200134786A1
• Filed: 10/31/2018
• Published: 04/30/2020
• Est. Priority Date: 10/31/2018
• Status: Active Grant

• Current Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Original Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Inventors: GONDEK, Jay S., Quintana, Jason M., Justel, Milan Crowley
• Granted Patent: US 10,885,612 B2
• Time in Patent Office: Days
• CPC Class Codes: G06T 2207/20192 Edge enhancement; Edge preservation
• CPC Class Codes: G06T 5/73 Deblurring; Sharpening
• CPC Class Codes: H04N 1/40012 Conversion of colour to monochrome
• CPC Class Codes: H04N 1/4092 Edge or detail enhancement

Abstract

In some examples, luminance-biased sharpening for thermal media printing may include converting an input image to a grayscale luminance representation. For each pixel of a plurality of specified pixels of the converted input image, a sharpening lightness value may be determined. Further, for each pixel of the plurality of specified pixels of the converted input image, a ratio of the sharpening lightness value to a corresponding original lightness value may be determined. Based on the determined ratio, a sharpened output image corresponding to the input image may be generated.

Claims

1. An apparatus comprising:

a processor; and

a non-transitory computer readable medium storing machine readable instructions that when executed by the processor cause the processor to;

convert an input image to a grayscale luminance representation;

determine, for each pixel of a plurality of specified pixels of the converted input image, a sharpening lightness value;

determine, for each pixel of the plurality of specified pixels of the converted input image, a ratio of the sharpening lightness value to a corresponding original lightness value; and

generate, based on the determined ratio, a sharpened output image corresponding to the input image.

2. The apparatus according to claim 1, wherein the instructions to determine, for each pixel of the plurality of specified pixels of the converted input image, the sharpening lightness value, are further to cause the processor to:

determine, for each pixel of the plurality of specified pixels of the converted input image and based on application of a monochrome un-sharp mask, the sharpening lightness value.

3. The apparatus according to claim 1, wherein the instructions to generate, based on the determined ratio, the sharpened output image corresponding to the input image, are further to cause the processor to:

multiply, for each pixel of the plurality of specified pixels of the converted image, an output pixel value by a corresponding value of the determined ratio.

4. The apparatus according to claim 1, wherein the instructions to generate, based on the determined ratio, the sharpened output image corresponding to the input image, are further to cause the processor to:

multiply, for each pixel of the plurality of specified pixels of the converted image, a corresponding value of the determined ratio by red (R), green (G), and blue (B) components of a color.

5. The apparatus according to claim 1, wherein the instructions to generate, based on the determined ratio, the sharpened output image corresponding to the input image, are further to cause the processor to:

scale, for each pixel of the plurality of specified pixels of the converted image, a luminance (Y) value of a Y, blue-difference chroma (C_B), and red-difference chroma (C_R) image representation by a corresponding value of the determined ratio.

6. The apparatus according to claim 1, wherein the instructions to generate, based on the determined ratio, the sharpened output image corresponding to the input image, are further to cause the processor to:

ascertain a dark ratio threshold value and a light ratio threshold value;

determine, for each pixel of the plurality of specified pixels of the converted image, whether the determined ratio is less than the dark ratio threshold value, or whether the determined ratio is greater than the light ratio threshold value;

for each pixel of the plurality of specified pixels of the converted image, based on a determination that the determined ratio is less than the dark ratio threshold value, change the determined ratio to the dark ratio threshold value; and

for each pixel of the plurality of specified pixels of the converted image, based on a determination that the determined ratio is greater than the light ratio threshold value, change the determined ratio to the light ratio threshold value.

7. The apparatus according to claim 6, wherein the dark ratio threshold value is different from the light ratio threshold value.

8. The apparatus according to claim 1, wherein the instructions to generate, based on the determined ratio, the sharpened output image corresponding to the input image, are further to cause the processor to:

ascertain a dark ratio threshold value;

determine, for each pixel of the plurality of specified pixels of the converted image, whether the determined ratio is less than the dark ratio threshold value; and

for each pixel of the plurality of specified pixels of the converted image, based on a determination that the determined ratio is less than the dark ratio threshold value, change the determined ratio to the dark ratio threshold value.

9. The apparatus according to claim 1, wherein the instructions to generate, based on the determined ratio, the sharpened output image corresponding to the input image, are further to cause the processor to:

ascertain a first set of threshold values that include a first dark ratio threshold value and a first light ratio threshold value;

ascertain a second set of threshold values that include a second dark ratio threshold value and a second light ratio threshold value;

analyze, for each pixel of the plurality of specified pixels of the converted image and for an edge in the input image that transitions from dark to light in a print direction, the determined ratio relative to the first set of threshold values; and

analyze, for each pixel of the plurality of specified pixels of the converted image and for an edge in the input image that transitions from light to dark in the print direction, the determined ratio relative to the second set of threshold values.

10. The apparatus according to claim 9, wherein the first dark ratio threshold value is different from the second dark ratio threshold value, and the first light ratio threshold value is different from the second light ratio threshold value.

11. A computer implemented method comprising:

converting an input image to a grayscale luminance representation;

determining, for each pixel of a plurality of specified pixels of the converted input image, a sharpening lightness value;

determining, for each pixel of the plurality of specified pixels of the converted input image, a ratio of the sharpening lightness value to a corresponding original lightness value;

multiplying, for each pixel of the plurality of specified pixels of the converted image, an output pixel value by a corresponding value of the determined ratio; and

generating, based on the multiplying, for each pixel of the plurality of specified pixels of the converted image, of the output pixel value by the corresponding value of the determined ratio, a sharpened output image corresponding to the input image.

12. The computer implemented method according to claim 11, wherein

generating, based on the multiplying, for each pixel of the plurality of specified pixels of the converted image, of the output pixel value by the corresponding value of the determined ratio, the sharpened output image corresponding to the input image further comprises:

ascertaining a dark ratio threshold value and a light ratio threshold value;

determining, for each pixel of the plurality of specified pixels of the converted image, whether the determined ratio is less than the dark ratio threshold value, or whether the determined ratio is greater than the light ratio threshold value;

for each pixel of the plurality of specified pixels of the converted image, based on a determination that the determined ratio is less than the dark ratio threshold value, changing the determined ratio to the dark ratio threshold value; and

for each pixel of the plurality of specified pixels of the converted image, based on a determination that the determined ratio is greater than the light ratio threshold value, changing the determined ratio to the light ratio threshold value.

13. The computer implemented method according to claim 11, wherein

generating, based on the multiplying, for each pixel of the plurality of specified pixels of the converted image, of the output pixel value by the corresponding value of the determined ratio, the sharpened output image corresponding to the input image further comprises:

ascertaining a first set of threshold values that include a first dark ratio threshold value and a first light ratio threshold value;

ascertaining a second set of threshold values that include a second dark ratio threshold value and a second light ratio threshold value;

analyzing, for each pixel of the plurality of specified pixels of the converted image and for an edge in the input image that transitions from dark to light in a print direction, the determined ratio relative to the first set of threshold values; and

analyzing, for each pixel of the plurality of specified pixels of the converted image and for an edge in the input image that transitions from light to dark in the print direction, the determined ratio relative to the second set of threshold values.

14. A non-transitory computer readable medium having stored thereon machine readable instructions, the machine readable instructions, when executed, cause a processor to:

convert an input image to a grayscale luminance representation;

determine, for each pixel of a plurality of specified pixels of the converted input image, a sharpening lightness value;

determine, for each pixel of the plurality of specified pixels of the converted input image, a ratio of the sharpening lightness value to a corresponding original lightness value; and

generate, based on the determined ratio, a sharpened output image corresponding to the input image by

multiplying, for each pixel of the plurality of specified pixels of the converted image, a corresponding value of the determined ratio by red (R), green (G), and blue (B) components of a color, or

scaling, for each pixel of the plurality of specified pixels of the converted image, a luminance (Y) value of a Y, blue-difference chroma (C_B), and red-difference chroma (C_R) image representation by the corresponding value of the determined ratio.

15. The non-transitory computer readable medium according to claim 14, wherein the machine readable instructions to generate, based on the determined ratio, the sharpened output image corresponding to the input image, when executed, further cause the processor to:

ascertain a dark ratio threshold value and a light ratio threshold value;

determine, for each pixel of the plurality of specified pixels of the converted image, whether the determined ratio is less than the dark ratio threshold value, or whether the determined ratio is greater than the light ratio threshold value;

for each pixel of the plurality of specified pixels of the converted image, based on a determination that the determined ratio is less than the dark ratio threshold value, change the determined ratio to the dark ratio threshold value; and

for each pixel of the plurality of specified pixels of the converted image, based on a determination that the determined ratio is greater than the light ratio threshold value, change the determined ratio to the light ratio threshold value.