Area based interpolation for image scaling

• US 5,889,895 A
• Filed: 05/19/1998
• Issued: 03/30/1999
• Est. Priority Date: 05/23/1995
• Status: Expired due to Term

• Current Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Original Assignee: Hewlett-Packard Company (HP Inc.)
• Inventors: Herley, Cormac, Wong, Ping Wah
• Primary Examiner(s): Vu, Kim Yen
• Assistant Examiner(s): Williams, Kimberly A.
• Application Number:
  US09/081,336
• Time in Patent Office: 315 Days
• Field of Search: 358/448, 382/232, 382/233, 382/264, 382/279, 382/299, 382/300
• US Class Current: 382/300
• CPC Class Codes: G06T 3/4007 based on interpolation, e.g. bilinear interpolation image demosaicing G06T3/4015; edge-driven or edge-based scaling G06T3/403

Abstract

A technique, referred to as area-based interpolation, performs image interpolation. The system determines a curve by the pixel value at a location by taking the integral of a curve over a small area, where the size of the area is determined by the sampling size of a sampling cell. When the image is resampled with respect to a sampling cell that has a finer spacing, the system integrates the polynomial using a finer integration area. In accordance with the invention, the relation between the reintegrated, resampled high resolution image and the low resolution image is a function of an up-sampler, followed by a linear filter. The coefficients of the filter are independent of the data, but are dependent on the family of curves used. If the system models by, for example, a third degree or fourth degree polynomial everywhere in the image, then that model determines the number of coefficients that are in the filter. Once the up-sampling factor and degree of the polynomial are determined, the filter coefficients are fixed, and can be calculated by solving a set of linear equations. It is not necessary to determine these values on an image-by-image basis. The system calculates the filter once and the consistency constraint is then satisfied for all image scaling.

Claims

1. A method for image scaling by area based interpolation, comprising the steps of:

deconvolving the data x_mn by low resolution sensor function, where x_mn is the output of a single sensor;

upsampling to a desired resolution;

convolving the up-sampled data by a high resolution sensor function; and

low pass filtering to remove spectral aliases.

2. An apparatus for image scaling by area based interpolation, comprising:

means for deconvolving the data x_mn by low resolution sensor function, where x_mn is the output of a single sensor;

a sampler for upsampling to a desired resolution;

means for convolving the up-sampled data by a high resolution sensor function; and

a low pass filter for removing spectral aliases.