/*! @file logcurve.c
 *
 *  @brief Implementation of functions used to do log conversion.
 *
 *  @version 1.0.0
 *
 *  (C) Copyright 2018 GoPro Inc (http://gopro.com/).
 *
 *  Licensed under either:
 *  - Apache License, Version 2.0, http://www.apache.org/licenses/LICENSE-2.0
 *  - MIT license, http://opensource.org/licenses/MIT
 *  at your option.
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */

#include "common.h"

uint16_t EncoderLogCurve[LOG_CURVE_TABLE_LENGTH];

uint16_t DecoderLogCurve[LOG_CURVE_TABLE_LENGTH];

void SetupDecoderLogCurve(void)
{
    int i;
    const int log_table_size = sizeof(DecoderLogCurve) / sizeof(DecoderLogCurve[0]);
    
    const int max_16_bit = (1 << 16) - 1;
    
    for( i = 0; i < log_table_size; i++ )
    {
        //input 12-bit, output 16-bit
        float input = i;
        float output = max_16_bit * (pow(113.0, input/4095.0) - 1.0)/112.0;
        
        DecoderLogCurve[i]  = minimum( (int)output, max_16_bit );
    }
}

void SetupEncoderLogCurve(void)
{
    int i;
    const int max_input_val = LOG_CURVE_TABLE_LENGTH - 1;
    
    for( i = 0; i < LOG_CURVE_TABLE_LENGTH; i++ )
    {
        //input 16-bit, output 12-bit
        float input = maximum( 0, i );
        float output = 4095.0 * (log10(input/max_input_val * 112.0 + 1.0)/log10(113));

        EncoderLogCurve[i]  = ( (uint16_t)output );
    }
}