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Cap Mask contrast factor at maximum contrast #1067

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Merged
jonoomph merged 1 commit into from
May 4, 2026
Merged

Cap Mask contrast factor at maximum contrast #1067

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2 changes: 1 addition & 1 deletion src/effects/Mask.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -75,7 +75,7 @@ std::shared_ptr<openshot::Frame> Mask::GetFrame(std::shared_ptr<openshot::Frame>
double brightness_value = brightness.GetValue(frame_number);

int brightness_adj = static_cast<int>(255 * brightness_value);
float contrast_factor = 20.0f / std::max(0.00001f, 20.0f - static_cast<float>(contrast_value));
float contrast_factor = 20.0f / std::max(0.5f, 20.0f - static_cast<float>(contrast_value));
const bool output_mask = replace_image;
const auto clamp_u8 = [](int value) -> unsigned char {
if (value < 0) return 0;
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20 changes: 20 additions & 0 deletions tests/Mask.cpp
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Expand Up @@ -103,6 +103,26 @@ TEST_CASE("Mask replace_image emits grayscale values", "[effect][mask_effect][re
CHECK(px1.alpha() == px1.red());
}

TEST_CASE("Mask maximum contrast keeps a narrow transition band", "[effect][mask_effect][contrast]") {
auto frame = std::make_shared<Frame>(1, 3, 1, "#000000");
auto image = frame->GetImage();
image->setPixelColor(0, 0, QColor(255, 0, 0, 255));
image->setPixelColor(1, 0, QColor(255, 0, 0, 255));
image->setPixelColor(2, 0, QColor(255, 0, 0, 255));

const std::string mask_path = create_mask_png({128, 129, 134});
Mask mask;
mask.Reader(new QtImageReader(mask_path));
mask.brightness = Keyframe(0.0);
mask.contrast = Keyframe(20.0);

auto out = mask.GetFrame(frame, 1);

CHECK(out->GetImage()->pixelColor(0, 0).alpha() == 127);
CHECK(out->GetImage()->pixelColor(1, 0).alpha() == 87);
CHECK(out->GetImage()->pixelColor(2, 0).alpha() == 0);
}

TEST_CASE("Mask accepts legacy reader json field", "[effect][mask_effect][json]") {
const std::string mask_path = create_mask_png({128});
QtImageReader reader(mask_path);
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