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backend: Don't enable Resample for unity scale #47

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Merged
merged 1 commit into from
Jul 25, 2025
Merged

backend: Don't enable Resample for unity scale #47

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14 changes: 10 additions & 4 deletions src/libpisp/backend/backend_prepare.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -617,10 +617,13 @@ void BackEnd::updateSmartResize()
be_config_.global.rgb_enables &= ~PISP_BE_RGB_ENABLE_DOWNSCALE(i);
}

pisp_be_resample_config resample;
pisp_be_resample_extra resample_extra;
memset(&resample, 0, sizeof(resample));
memset(&resample_extra, 0, sizeof(resample_extra));
// Don't resample by unity: it needlessly reduces bit-depth, and can over-sharpen
if (resampler_input_width == resampler_output_width &&
resampler_input_height == resampler_output_height)
{
be_config_.global.rgb_enables &= ~PISP_BE_RGB_ENABLE_RESAMPLE(i);
continue;
}

// Finally program up the resampler block.
// If the following conditions are met:
Expand All @@ -634,6 +637,9 @@ void BackEnd::updateSmartResize()
// on image quality for larger downscale factors.
double scale_factor_x = (double)(resampler_input_width - 1) / (resampler_output_width - 1);
double scale_factor_y = (double)(resampler_input_height - 1) / (resampler_output_height - 1);
pisp_be_resample_config resample = {};
pisp_be_resample_extra resample_extra = {};

if (scale_factor_x > 2.1 &&
scale_factor_x < scale_factor_y * 1.1 && scale_factor_y < scale_factor_x * 1.1)
{
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