gis-tools-ts/dist/readers/image/lanczos.d.ts

A collection of geospatial tools primarily designed for WGS84, Web Mercator, and S2.

/**
 * # Lanczos Resampling
 *
 * ## Description
 * Perform a 2D Lanczos filter on an image. the Lanczos resampler creates some regions that are
 * darker than any in the original and others that are lighter than any in the original. This
 * Fourier transform method is useful in spatial/GIS applications, especially downscaling raster
 * data.
 *
 * ## Usage
 * ```ts
 * import sharp from 'sharp';
 * import { lanczos, createImage } from 'gis-tools-ts';
 * // pull in the image you want to downscale
 * const pattern = await sharp('./pattern.png')
 * .raw()
 * .toBuffer({ resolveWithObject: true });
 * // setup the destianation image
 * const patternHalf = createImage(4, 4);
 * // resize down into patternHalf
 * lanczos(pattern, patternHalf);
 * ```
 *
 * ## Links
 * - https://en.wikipedia.org/wiki/Lanczos_algorithm
 * - https://en.wikipedia.org/wiki/Lanczos_resampling
 * - https://gis.stackexchange.com/questions/10931/what-is-lanczos-resampling-useful-for-in-a-spatial-context
 * - https://icess.eri.ucsb.edu/gem/Duchon_1979_JAM_Lanczos.pdf
 * @param source - the source image
 * @param dest - the destination image
 * @param sx - source starting x point [Default: 0]
 * @param sy - source starting y point [Default: 0]
 * @param sw - source width to use [Default: source width - sx]
 * @param sh - source height to use [Default: source height - sy]
 * @param dx - destination starting x point [Default: 0]
 * @param dy - destination starting y point [Default: 0]
 * @param dw - destination width to use [Default: destination width - dx]
 * @param dh - destination height to use [Default: destination height - dy]
 * @param use2 - use 2nd lanczos filter instead of 3rd [Default: false]
 */
export declare function lanczos(source: ImageData, dest: ImageData, sx?: number, sy?: number, sw?: number, sh?: number, dx?: number, dy?: number, dw?: number, dh?: number, use2?: boolean): void;
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