78 lines
3.0 KiB
C
78 lines
3.0 KiB
C
/****************************************************************************
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* libs/libnx/nxglib/nxglib_rgb2yuv.c
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*
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* SPDX-License-Identifier: Apache-2.0
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*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership. The
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* ASF licenses this file to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance with the
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* License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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*
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****************************************************************************/
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/****************************************************************************
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* Included Files
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****************************************************************************/
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#include <nuttx/config.h>
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#include <stdint.h>
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#include <debug.h>
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#include <fixedmath.h>
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#include <nuttx/nx/nxglib.h>
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/****************************************************************************
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* Pre-Processor Definitions
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****************************************************************************/
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#define b16_P0813 0x000014d0 /* 0.0813 */
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#define b16_P1140 0x00001d2f /* 0.1140 */
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#define b16_P1687 0x00002b30 /* 0.1687 */
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#define b16_P2990 0x00004c8b /* 0.2990 */
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#define b16_P3313 0x000054d0 /* 0.3313 */
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#define b16_P4187 0x00006b30 /* 0.4187 */
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#define b16_P5000 0x00008000 /* 0.5000 */
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#define b16_P5870 0x00009646 /* 0.5870 */
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#define b16_128P0 0x00800000 /* 128.0 */
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/****************************************************************************
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* Public Functions
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****************************************************************************/
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/****************************************************************************
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* Name: nxgl_rgb2yuv
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*
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* Description:
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* Convert 8-bit RGB triplet to 8-bit YUV triplet
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*
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****************************************************************************/
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void nxgl_rgb2yuv(uint8_t r, uint8_t g, uint8_t b,
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uint8_t *y, uint8_t *u, uint8_t *v)
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{
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/* Per the JFIF specification:
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*
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* Y = (0.2990 * R) + (0.5870 * G) + (0.1140 * B)
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* U = 128 - (0.1687 * R) - (0.3313 * G) + (0.5000 * B)
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* V = 128 + (0.5000 * R) - (0.4187 * G) - (0.0813 * B);
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*/
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*y = (uint8_t)b16toi(b16muli(b16_P2990, r) +
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b16muli(b16_P5870, g) + b16muli(b16_P1140, b));
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*u = (uint8_t)b16toi(b16_128P0 - b16muli(b16_P1687, r) -
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b16muli(b16_P3313, g) + b16muli(b16_P5000, b));
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*v = (uint8_t)b16toi(b16_128P0 + b16muli(b16_P5000, r) -
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b16muli(b16_P4187, g) - b16muli(b16_P0813, b));
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}
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