114 lines
3.3 KiB
C
114 lines
3.3 KiB
C
|
|
/* ***** BEGIN LICENSE BLOCK *****
|
|
* Version: MPL 1.1/GPL 2.0/LGPL 2.1
|
|
*
|
|
* 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
|
|
* the License. You may obtain a copy of the License at
|
|
* http://www.mozilla.org/MPL/
|
|
*
|
|
* Software distributed under the License is distributed on an "AS IS" basis,
|
|
* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
|
|
* 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.
|
|
*
|
|
* Contributor(s):
|
|
*
|
|
* Alternatively, the contents of this file may be used under the terms of
|
|
* either the GNU General Public License Version 2 or later (the "GPL"), or
|
|
* the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
|
|
* in which case the provisions of the GPL or the LGPL are applicable instead
|
|
* of those above. If you wish to allow use of your version of this file only
|
|
* under the terms of either the GPL or the LGPL, and not to allow others to
|
|
* use your version of this file under the terms of the MPL, indicate your
|
|
* decision by deleting the provisions above and replace them with the notice
|
|
* and other provisions required by the GPL or the LGPL. If you do not delete
|
|
* the provisions above, a recipient may use your version of this file under
|
|
* the terms of any one of the MPL, the GPL or the LGPL.
|
|
*
|
|
* ***** END LICENSE BLOCK ***** */
|
|
|
|
|
|
#include <stdint.h>
|
|
#include <cairo/cairo.h>
|
|
|
|
/*
|
|
* Arbitrary hash function whhich maps ALL 32-bit numbers onto 24-bit numbers
|
|
* evenly, while guaranteeing that all 24-bit numbers are mapped onto
|
|
* themselves.
|
|
*/
|
|
int _guac_hash_32to24(int value) {
|
|
|
|
/* Grab highest-order byte */
|
|
int upper = value & 0xFF000000;
|
|
|
|
/* XOR upper with lower three bytes, truncate to 24-bit */
|
|
return
|
|
(value & 0xFFFFFF)
|
|
^ (upper >> 8)
|
|
^ (upper >> 16)
|
|
^ (upper >> 24);
|
|
|
|
}
|
|
|
|
/**
|
|
* Rotates a given 32-bit integer by N bits.
|
|
*
|
|
* NOTE: We probably should check for available bitops.h macros first.
|
|
*/
|
|
unsigned int _guac_rotate(unsigned int value, int amount) {
|
|
|
|
/* amount = amount % 32 */
|
|
amount &= 0x1F;
|
|
|
|
/* Return rotated amount */
|
|
return (value >> amount) | (value << (32 - amount));
|
|
|
|
}
|
|
|
|
int guac_hash_surface(cairo_surface_t* surface) {
|
|
|
|
/* Init to zero */
|
|
int hash_value = 0;
|
|
|
|
int x, y;
|
|
|
|
/* Get image data and metrics */
|
|
unsigned char* data = cairo_image_surface_get_data(surface);
|
|
int width = cairo_image_surface_get_width(surface);
|
|
int height = cairo_image_surface_get_height(surface);
|
|
int stride = cairo_image_surface_get_stride(surface);
|
|
|
|
for (y=0; y<height; y++) {
|
|
|
|
/* Get current row */
|
|
uint32_t* row = (uint32_t*) data;
|
|
data += stride;
|
|
|
|
for (x=0; x<width; x++) {
|
|
|
|
/* Get color at current pixel */
|
|
int color = *row;
|
|
row++;
|
|
|
|
/* Compute next hash */
|
|
hash_value =
|
|
_guac_rotate(hash_value, 1) ^ _guac_hash_32to24(color);
|
|
|
|
}
|
|
|
|
} /* end for each row */
|
|
|
|
/* Done */
|
|
return hash_value;
|
|
|
|
}
|
|
|