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Add support to normalise for lower and upper percentiles (#3583)

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This commit is contained in:
LachlanNewman
2023-03-01 19:10:44 +08:00
committed by Lovell Fuller
parent 1eefd4e562
commit d7776e3b98
9 changed files with 140 additions and 22 deletions
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9
src/operations.cc
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@@ -6,7 +6,6 @@
#include <memory>
#include <tuple>
#include <vector>
#include <vips/vips8>
#include "common.h"
@@ -46,7 +45,7 @@ namespace sharp {
/*
* Stretch luminance to cover full dynamic range.
*/
VImage Normalise(VImage image) {
VImage Normalise(VImage image, int const lower, int const upper) {
// Get original colourspace
VipsInterpretation typeBeforeNormalize = image.interpretation();
if (typeBeforeNormalize == VIPS_INTERPRETATION_RGB) {
@@ -56,9 +55,11 @@ namespace sharp {
VImage lab = image.colourspace(VIPS_INTERPRETATION_LAB);
// Extract luminance
VImage luminance = lab[0];
// Find luminance range
int const min = luminance.percent(1);
int const max = luminance.percent(99);
int const min = lower == 0 ? luminance.min() : luminance.percent(lower);
int const max = upper == 100 ? luminance.max() : luminance.percent(upper);
if (std::abs(max - min) > 1) {
// Extract chroma
VImage chroma = lab.extract_band(1, VImage::option()->set("n", 2));