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/****************************************************************************
* graphics/color/nxglib_rgb2yuv.c
*
* Copyright (C) 2008 Gregory Nutt. All rights reserved.
* Author: Gregory Nutt <spudmonkey@racsa.co.cr>
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
* 3. Neither the name NuttX nor the names of its contributors may be
* used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
* OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
* AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
*
****************************************************************************/
/****************************************************************************
* Included Files
****************************************************************************/
#include <nuttx/config.h>
#include <sys/types.h>
#include <debug.h>
#include <fixedmath.h>
#include <nuttx/nxglib.h>
/****************************************************************************
* Pre-Processor Definitions
****************************************************************************/
#define b16_P0813 0x000014d0 /* 0.0813 */
#define b16_P1140 0x00001d2f /* 0.1140 */
#define b16_P1687 0x00002b30 /* 0.1687 */
#define b16_P2990 0x00004c8b /* 0.2990 */
#define b16_P3313 0x000054d0 /* 0.3313 */
#define b16_P4187 0x00006b30 /* 0.4187 */
#define b16_P5000 0x00008000 /* 0.5000 */
#define b16_P5870 0x00009646 /* 0.5870 */
#define b16_128P0 0x00800000 /* 128.0 */
/****************************************************************************
* Private Types
****************************************************************************/
/****************************************************************************
* Private Function Prototypes
****************************************************************************/
/****************************************************************************
* Private Data
****************************************************************************/
/****************************************************************************
* Private Functions
****************************************************************************/
/****************************************************************************
* Public Functions
****************************************************************************/
/****************************************************************************
* Name: nxgl_rgb2yuv
*
* Description:
* Convert 8-bit RGB triplet to 8-bit YUV triplet
*
****************************************************************************/
void nxgl_rgb2yuv(ubyte r, ubyte g, ubyte b, ubyte *y, ubyte *u, ubyte *v)
{
/* Per the JFIF specification:
*
* Y = (0.2990 * R) + (0.5870 * G) + (0.1140 * B)
* U = 128 - (0.1687 * R) - (0.3313 * G) + (0.5000 * B)
* V = 128 + (0.5000 * R) - (0.4187 * G) - (0.0813 * B);
*/
*y = (ubyte)b16toi(b16muli(b16_P2990, r) + b16muli(b16_P5870, g) + b16muli(b16_P1140, b));
*u = (ubyte)b16toi(b16_128P0 - b16muli(b16_P1687, r) - b16muli(b16_P3313, g) + b16muli(b16_P5000, b));
*v = (ubyte)b16toi(b16_128P0 + b16muli(b16_P5000, r) - b16muli(b16_P4187, g) - b16muli(b16_P0813, b));
}
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