guacamole-spice-protocol/libguac/include/hash.h

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 * Version: MPL 1.1/GPL 2.0/LGPL 2.1
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 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (the "License"); you may not use this file except in compliance with
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 *
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 * for the specific language governing rights and limitations under the
 * License.
 *
 * The Original Code is libguac.
 *
 * The Initial Developer of the Original Code is
 * Michael Jumper.
 * Portions created by the Initial Developer are Copyright (C) 2010
 * the Initial Developer. All Rights Reserved.
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 *
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#ifndef _GUAC_HASH_H
#define _GUAC_HASH_H

#include <cairo/cairo.h>

/**
 * A wrapper for a Cairo surface which allows fast image queries (linear time
 * in the size of the query image). Given an arbitrary input image, the first
 * occurence of that image within the contained surface can be found quickly.
 */
typedef struct guac_indexed_surface {

    /**
     * The Cairo surface which is indexed.
     */
    cairo_surface_t* surface;

} guac_indexed_surface;

typedef struct guac_indexed_surface_subimage {

    /**
     * The indexed surface this subimage is a part of.
     */
    guac_indexed_surface* surface;

    /**
     * The X coordinate of the upper-left point of the rectangle
     * of the subimage.
     */
    int x;

    /**
     * The Y coordinate of the upper-left point of the rectangle
     * of the subimage.
     */
    int y;

    /**
     * The width of the subimage in pixels.
     */
    int width;

    /**
     * The height of the subimage in pixels.
     */
    int height;

} guac_indexed_surface_subimage;

/**
 * Creates a new indexed surface, using the given surface as the image data
 * source. The given surface will be made searchable such that queries of
 * images which are at least the given width and height can be resolved
 * quickly.
 *
 * @param surface The Cairo surface to index.
 * @param min_width The minimum image width to allow for queries.
 * @param min_height The minimum image height to allow for queries.
 * @return A newly allocated guac_indexed_surface.
 */
guac_indexed_surface* guac_indexed_surface_alloc(cairo_surface_t* surface,
        int min_width, int min_height);

/**
 * Frees the given indexed surface.
 *
 * @param surface The guac_indexed_surface to free.
 */
void guac_indexed_surface_free(guac_indexed_surface* surface);

/**
 * Given an indexed surface and a query image, finds the rectangle of the
 * subimage of the indexed surface containing exactly the query image (if
 * any) and saves the result.
 *
 * @param surface The guac_indexed_surface to query.
 * @param query The image to search for within the indexed surface.
 * @param result A pointer to an already-allocated
 *               guac_indexed_surface_subimage which will be modified
 *               to contain the result if a result is found.
 * @return Non-zero if the given query image was found within the indexed
 *         surface, in which case the result will be stored in the given
 *         guac_indexed_surface_subimage, or zero if the query image could
 *         not be found, in which case the given guac_indexed_surface_subimage
 *         will not be modified.
 */
int guac_indexed_surface_find(guac_indexed_surface* surface,
        cairo_surface_t* query, guac_indexed_surface_subimage* result);

/**
 * Produces a 24-bit hash value from all pixels of the given surface. The
 * surface provided must be RGB or ARGB with each pixel stored in 32 bits.
 * The hashing algorithm used is a variant of the cyclic polynomial rolling
 * hash.
 *
 * @param surface The Cairo surface to hash.
 * @return An arbitrary 24-bit unsigned integer value intended to be well
 *         distributed across different images.
 */
unsigned int guac_hash_surface(cairo_surface_t* surface);

/**
 * Given two Cairo surfaces, returns zero if the data contained within each
 * is identical, and a positive or negative value if the value of the first
 * is found to be lexically greater or less than the second respectively.
 *
 * @param a The first Cairo surface to compare.
 * @param b The Cairo surface to compare the first surface against.
 * @return Zero if the data contained within each is identical, and a positive
 *         or negative value if the value of the first is found to be lexically
 *         greater or less than the second respectively.
 */
int guac_surface_cmp(cairo_surface_t* a, cairo_surface_t* b);

#endif