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/*! @file dequantize.c
*
* @brief Implementation of inverse quantization functions
*
* @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 "headers.h"
// Not using midpoint correction in dequantization
static const int midpoint = 0;
/*!
@brief Dequantize a band with the specified dimensions
The companding curve is inverted and the value is multiplied by the
quantization value that was used by the encoder to compress the band.
*/
CODEC_ERROR DequantizeBandRow16s(PIXEL *input, int width, int quantization, PIXEL *output)
{
int column;
// Undo quantization in the entire row
for (column = 0; column < width; column++)
{
int32_t value = input[column];
// Invert the companding curve (if any)
value = UncompandedValue(value);
// Dequantize the absolute value
if (value > 0)
{
value = (quantization * value) + midpoint;
}
else if (value < 0)
{
value = neg(value);
value = (quantization * value) + midpoint;
value = neg(value);
}
// Store the dequantized coefficient
output[column] = ClampPixel(value);
}
return CODEC_ERROR_OKAY;
}
/*!
@brief This function dequantizes the pixel value
The inverse companding curve is applied to convert the pixel value
to its quantized value and then the pixel value is multiplied by
the quantization parameter.
*/
PIXEL DequantizedValue(int32_t value, int quantization)
{
// Invert the companding curve (if any)
value = UncompandedValue(value);
// Dequantize the absolute value
if (value > 0)
{
value = (quantization * value) + midpoint;
}
else if (value < 0)
{
value = neg(value);
value = (quantization * value) + midpoint;
value = neg(value);
}
return ClampPixel(value);
}
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