Filtering stylus strokes

• US 9,898,099 B1
• Filed: 12/15/2014
• Issued: 02/20/2018
• Est. Priority Date: 12/15/2014
• Status: Expired due to Fees

• Current Assignee: Amazon Technologies, Inc. (Amazon.com, Inc.)
• Original Assignee: Amazon Technologies, Inc. (Amazon.com, Inc.)
• Inventors: Schubert, Heidi Christine, Gerhard, Lutz
• Primary Examiner(s): Mengistu, Amare
• Assistant Examiner(s): Nadkarni, Sarvesh J
• Application Number:
  US14/570,727
• Time in Patent Office: 1,163 Days
• Field of Search: None
• CPC Class Codes: G06F 18/00 Pattern recognition
• CPC Class Codes: G06F 3/03545 Pens or stylus
• CPC Class Codes: G06F 3/041 Digitisers, e.g. for touch screens or touch pads, characterised by the transducing means
• CPC Class Codes: G06F 3/04162 for exchanging data with external devices, e.g. smart pens, via the digitiser sensing hardware
• CPC Class Codes: G06F 3/04883 for inputting data by handwriting, e.g. gesture or text
• CPC Class Codes: G06V 30/1423 the instrument generating sequences of position coordinates corresponding to handwriting preprocessing or recognising digital ink G06V30/32
• CPC Class Codes: G06V 30/347 Sampling; Contour coding; Stroke extraction

Abstract

Devices, systems and methods are disclosed for processing stylus interactions with a device and drawing the results of those interactions in a manner that reduces noise and latency. This includes selecting a filter based on a velocity of an input, the velocity determined by comparing coordinates and timestamps associated with the input events. A first filter may be determined using previous input events to reduce latency and a second filter may be determined using previous and subsequent input events to improve accuracy of the filter selection. An output may be generated using the first filter and/or the second filter to combine the benefits of the reduced latency and the increased accuracy.

Claims

1. A computer-implemented method for displaying a line corresponding to contact between a stylus and a device, the method comprising:

determining a plurality of input events corresponding to a stroke input, the plurality of input events corresponding to multiple points of contact on a display of the device, each of the multiple points of contact having respective coordinates at which the display detects contact;

identifying some of the plurality of input events as first input events, the first input events including a selected input event;

identifying some of the plurality of input events as second input events, the second input events occurring at times prior to a time of the selected input event;

determining a second velocity of the stroke input based on the second input events;

determining a first velocity of the stroke input based on the first input events;

determining a second velocity of the stroke input based on the second input events;

selecting a first cutoff frequency of a first filter based on the first average velocity;

selecting a second cutoff frequency of a second filter based on the second average velocity;

removing high frequency components of the plurality of input events using the first filter to generate first filtered inputs, the high frequency components having a frequency above the first cutoff frequency;

removing high frequency components of the plurality of input events using the second filter to generate second filtered inputs, the high frequency components having a frequency above the second cutoff frequency;

generating a first output including the first filtered inputs, the first output being a first filtered version of the stroke input;

displaying the output on the touchscreen display; and

replacing portions of the first output originally corresponding to the first filtered inputs with the second filtered inputs to create a second filtered version of the stroke input.

2. The computer-implemented method of claim 1, wherein the identifying further comprises:

identifying the selected input event as a most recent input event of the plurality of input events,

wherein the first input events is a determined number of input events prior to and including the most recent input event.

3. The computer-implemented method of claim 1, further comprising:

identifying some of the plurality of input events as second input events;

determining a third velocity of the stylus between a first input event and a second input event of the second input events;

determining a fourth velocity of the stylus between the second input event and a third input event of the second input events;

determining a second average velocity based on the third velocity and the fourth velocity;

selecting a second cutoff frequency of a second filter based on the second average velocity;

removing high frequency components of the plurality of input events using the second filter to generate second filtered inputs, the high frequency components having a frequency above the second cutoff frequency;

generating a second output including the second filtered inputs, the output being a second filtered version of the stylus stroke; and

displaying the second output on the touchscreen display after displaying the first output.

4. A computer-implemented method, comprising:

determining a plurality of input events corresponding to a stroke input, the plurality of input events corresponding to multiple points of contact on a display of a device, each of the multiple points of contact having respective coordinates at which the display detects contact;

identifying some of the plurality of input events as first input events, the first input events including a selected input event;

identifying some of the plurality of input events as second input events, the second input events occurring at times prior to a time of the selected input event;

determining a first velocity of the stroke input based on the first input events;

determining a second velocity of the stroke input based on the second input events;

selecting a first cutoff frequency of a first filter based on the first velocity

selecting a second cutoff frequency of a second filter based on the second velocity;

removing first high frequency components of the plurality of input events using the first filter to generate first filtered inputs, the first high frequency components having a frequency above the first cutoff frequency;

removing second high frequency components of the plurality of input events using the second filter to generate second filtered inputs, the second high frequency components having a frequency above the second cutoff frequency;

generating a first output including the first filtered inputs;

generating a second output including the second filtered inputs;

displaying the first output on the device; and

replacing portions of the first output originally corresponding to the first filtered inputs with the second filtered inputs.

5. The computer-implemented method of claim 4, wherein the identifying further comprises:

identifying the selected input event as a most recent input event of the plurality of input events,

wherein the first input events are a determined number of input events of the plurality of input events prior to and including the most recent input event.

6. The computer-implemented method of claim 4, wherein the identifying further comprises:

identifying a center input event of the plurality of input events,

wherein the second input events are a determined number of input events of the plurality of input events centered on the center input event.

7. The computer-implemented method of claim 4, further comprising:

identifying some of the plurality of input events as second input events;

determining a second velocity of the stroke input based on the second input events;

selecting a second cutoff frequency of a second filter based on the second velocity, the second filter being a low pass filter;

removing high frequency components of the plurality of input events using the second filter to generate second filtered inputs, the high frequency components having a frequency above the second cutoff frequency;

generating a second output including the second filtered inputs; and

displaying the second output after the output.

8. The computer-implemented method of claim 7, wherein

the identifying the first input events further comprises:

identifying a most recent input event of the plurality of input events; and

identifying the first input events, the first input events being a first number of input events prior to and including the most recent input event, and

the identifying the second input events further comprises;

identifying a center input event of the plurality of input events, the center input event previous to the most recent input event; and

identifying the second input events, the second input events being a second number of input events centered on the center input event.

9. The computer-implemented method of claim 4, wherein

a velocity of the stroke input includes a first component along a first axis of the display and a second component along a second axis of the display, and the first velocity is based only on the first component.

10. The computer-implemented method of claim 4, further comprising determining that the stroke input is complete.

11. The computer-implemented method of claim 4, further comprising selecting a new first cutoff frequency after expiration of a time interval.

12. The computer-implemented method of claim 4, further comprising selecting a new first cutoff frequency based on a change in the first cutoff velocity.

13. The computer-implemented method of claim 4, further comprising changing a value of the first cutoff frequency from a first frequency value to a second frequency value by transitioning to at least one intermediate frequency value between the first frequency value and the second frequency value.

14. The computer-implemented method of claim 4, wherein the second cutoff frequency is lower than the first cutoff frequency.

15. A computing device, comprising:

a touchscreen;

at least one processor;

a memory device including instructions operable to be executed by the at least one processor to cause the device to;

determine a plurality of input events corresponding to a stroke input, the plurality of input events corresponding to multiple points of contact on the touchscreen, each of the multiple points of contact having respective coordinates at which the touchscreen detects contact;

identify some of the plurality of input events as first input events, the first input events including a selected input event;

identify some of the plurality of input events as second input events, the second input events occurring at times prior to a time of the selected input event

determine a first velocity of the stroke input based on the first input events;

determine a second velocity of the stroke input based on the second input events;

select a first cutoff frequency of a first filter based on the first velocity

select a second cutoff frequency of a second filter based on the second velocity;

remove high frequency components of the plurality of input events using the first filter to generate first filtered inputs, the high frequency components having a frequency above the first cutoff frequency;

remove high frequency components of the plurality of input events using the second filter to generate second filtered inputs, the high frequency components having a frequency above the second cutoff frequency;

generate a first output including the first filtered inputs;

generate a second output including the second filtered inputs;

display the first output on the device; and

replace portions of the first output originally corresponding to the first filtered inputs with the second filtered inputs.

16. The device of claim 15, wherein the instructions further configure the system to:

identify the selected input event as a most recent input event of the plurality of input events,

wherein the first input events are a determined number of input events of the plurality of input events prior to and including the most recent input event.

17. The device of claim 15, wherein the instructions further configure the system to:

identify a center input event of the plurality of input events,

wherein the second input events are a determined number of input events of the plurality of input events centered on the center input event.

18. The device of claim 15, wherein the instructions further configure the system to:

identify some of the plurality of input events as second input events;

determine a second velocity of the stroke input based on the second input events;

select a second cutoff frequency of a second filter based on the second velocity;

remove high frequency components of the plurality of input events using the second filter to generate second filtered inputs, the high frequency components having a frequency above the second cutoff frequency;

generate a second output including the second filtered inputs; and

display the second output after the output.

19. The device of claim 18, wherein the instructions further configure the system to:

identify a most recent input event of the plurality of input events; and

identify the first input events, the first input events being a first number of input events prior to and including the most recent input event;

identify a center input event of the plurality of input events, the center input event previous to the most recent input event; and

identify the second input events, the second input events being a second number of input events centered on the center input event.

20. The device of claim 15, wherein:

a velocity of the stroke input includes a first component along a first axis of the touchscreen and a second component along a second axis of the touchscreen, and

the first velocity is based only on the first component.

21. The device of claim 15, wherein the instructions further configure the system to determine that the stroke input is complete.

22. The device of claim 15, wherein the instructions further configure the system to select a new first cutoff frequency after expiration of a time interval.

23. The device of claim 15, wherein the instructions further configure the system to select a new first cutoff frequency based on a change in the first cutoff velocity.

24. The device of claim 15, wherein the instructions further configure the system to change a value of the first cutoff frequency from a first frequency value to a second frequency value by transitioning to at least one intermediate frequency value between the first frequency value and the second frequency value.

25. The device of claim 15, wherein the second cutoff frequency is lower than the first cutoff frequency.