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genesys: Improve gain calibration on GL843

merge-requests/97/head
Povilas Kanapickas 2019-07-02 23:30:50 +03:00
rodzic 8d3369f68e
commit af0f8e7e46
1 zmienionych plików z 13 dodań i 7 usunięć
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20
backend/genesys_gl843.cc
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@ -3574,7 +3574,6 @@ gl843_coarse_gain_calibration(Genesys_Device * dev, const Genesys_Sensor& sensor
int total_size;
int i, j, channels;
SANE_Status status = SANE_STATUS_GOOD;
int max[3];
float coeff;
int val, lines;
int resolution;
@ -3671,7 +3670,7 @@ gl843_coarse_gain_calibration(Genesys_Device * dev, const Genesys_Sensor& sensor
/* average value on each channel */
for (j = 0; j < channels; j++)
{
max[j] = 0;
std::vector<uint16_t> values;
// FIXME: start from the second line because the first line often has artifacts. Probably
// caused by unclean cleanup of previous scans
for (i = pixels/4 + pixels; i < (pixels*3/4) + pixels; i++)
@ -3695,9 +3694,16 @@ gl843_coarse_gain_calibration(Genesys_Device * dev, const Genesys_Sensor& sensor
val = line[i * channels + j];
}
max[j] += val;
values.push_back(val);
}
max[j] = max[j] / (pixels/2);
// pick target value at 95th percentile of all values. There may be a lot of black values
// in transparency scans for example
std::sort(values.begin(), values.end());
uint16_t target_value = values[unsigned((values.size() - 1) * 0.95)];
if (bpp == 16) {
target_value /= 256;
}
/* the flow of data through the frontend ADC is as follows (see e.g. VM8192 datasheet)
input
@ -3718,7 +3724,7 @@ gl843_coarse_gain_calibration(Genesys_Device * dev, const Genesys_Sensor& sensor
{PGA} = 283 * (1 - {output} / {target output})
*/
float gain = ((float) max[j] / (calib_sensor.gain_white_ref*coeff));
float gain = ((float) target_value / (calib_sensor.gain_white_ref*coeff));
int code = 283 * (1 - gain);
if (code > 255)
code = 255;
@ -3726,8 +3732,8 @@ gl843_coarse_gain_calibration(Genesys_Device * dev, const Genesys_Sensor& sensor
code = 0;
dev->frontend.set_gain(j, code);
DBG(DBG_proc, "%s: channel %d, max=%d, gain = %f, setting:%d\n", __func__, j, max[j], gain,
code);
DBG(DBG_proc, "%s: channel %d, max=%d, gain = %f, setting:%d\n", __func__, j, target_value,
gain, code);
}
if (dev->model->is_cis) {