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Add experimental entropy field to stats response

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This commit is contained in:
Lovell Fuller
2018-08-06 15:41:27 +01:00
parent 532de4ecab
commit 25bd2cea3e
5 changed files with 32 additions and 9 deletions
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19
src/stats.cc
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@@ -59,7 +59,6 @@ class StatsWorker : public Nan::AsyncWorker {
using sharp::MaximumImageAlpha;
vips::VImage image;
vips::VImage stats;
sharp::ImageType imageType = sharp::ImageType::UNKNOWN;
try {
@@ -69,9 +68,8 @@ class StatsWorker : public Nan::AsyncWorker {
}
if (imageType != sharp::ImageType::UNKNOWN) {
try {
stats = image.stats();
int bands = image.bands();
double const max = MaximumImageAlpha(image.interpretation());
vips::VImage stats = image.stats();
int const bands = image.bands();
for (int b = 1; b <= bands; b++) {
ChannelStats cStats(static_cast<int>(stats.getpoint(STAT_MIN_INDEX, b).front()),
static_cast<int>(stats.getpoint(STAT_MAX_INDEX, b).front()),
@@ -83,11 +81,15 @@ class StatsWorker : public Nan::AsyncWorker {
static_cast<int>(stats.getpoint(STAT_MAXY_INDEX, b).front()));
baton->channelStats.push_back(cStats);
}
// alpha layer is there and the last band i.e. alpha has its max value greater than 0)
if (sharp::HasAlpha(image) && stats.getpoint(STAT_MIN_INDEX, bands).front() != max) {
baton->isOpaque = false;
// Image is not opaque when alpha layer is present and contains a non-mamixa value
if (sharp::HasAlpha(image)) {
double const minAlpha = static_cast<double>(stats.getpoint(STAT_MIN_INDEX, bands).front());
if (minAlpha != MaximumImageAlpha(image.interpretation())) {
baton->isOpaque = false;
}
}
// Estimate entropy via histogram of greyscale value frequency
baton->entropy = std::abs(image.colourspace(VIPS_INTERPRETATION_B_W)[0].hist_find().hist_entropy());
} catch (vips::VError const &err) {
(baton->err).append(err.what());
}
@@ -130,6 +132,7 @@ class StatsWorker : public Nan::AsyncWorker {
Set(info, New("channels").ToLocalChecked(), channels);
Set(info, New("isOpaque").ToLocalChecked(), New<v8::Boolean>(baton->isOpaque));
Set(info, New("entropy").ToLocalChecked(), New<v8::Number>(baton->entropy));
argv[1] = info;
}

4
src/stats.h
View File

@@ -51,12 +51,14 @@ struct StatsBaton {
// Output
std::vector<ChannelStats> channelStats;
bool isOpaque;
double entropy;
std::string err;
StatsBaton():
input(nullptr),
isOpaque(true)
isOpaque(true),
entropy(0.0)
{}
};