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added a HDR demo executable (Python and C++)
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‎.gitignore‎

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@@ -24,6 +24,11 @@ example_icons.bc
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example_icons.js
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example_icons.wasm
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example_icons.exe
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example_hdr
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example_hdr.bc
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example_hdr.js
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example_hdr.wasm
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example_hdr.exe
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icons
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*~
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nanogui*.so

‎CMakeLists.txt‎

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@@ -546,8 +546,10 @@ if (NANOGUI_BUILD_EXAMPLES)
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add_executable(example3 src/example3.cpp)
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add_executable(example4 src/example4.cpp)
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add_executable(example_icons src/example_icons.cpp)
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add_executable(example_hdr src/example_hdr.cpp)
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target_link_libraries(example1 nanogui)
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target_link_libraries(example_hdr nanogui)
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target_link_libraries(example2 nanogui)
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target_link_libraries(example3 nanogui ${NANOGUI_LIBS}) # For OpenGL
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target_link_libraries(example4 nanogui)

‎src/example_hdr.cpp‎

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#include <nanogui/screen.h>
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#include <nanogui/window.h>
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#include <nanogui/layout.h>
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#include <nanogui/label.h>
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#include <nanogui/combobox.h>
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#include <nanogui/imageview.h>
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#include <nanogui/texture.h>
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#include <nanogui/chroma.h>
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#include <algorithm>
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#include <cmath>
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#include <vector>
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using namespace nanogui;
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using namespace nanogui::ituth273;
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struct PrimaryEntry {
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ColorPrimaries primary;
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const char* name;
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};
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static const PrimaryEntry primary_table[] = {
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{ ColorPrimaries::BT2020, "BT2020" },
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{ ColorPrimaries::BT470BG, "BT470BG" },
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{ ColorPrimaries::BT470M, "BT470M" },
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{ ColorPrimaries::BT709, "BT709" },
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{ ColorPrimaries::Film, "Film" },
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{ ColorPrimaries::SMPTE170M, "SMPTE170M" },
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{ ColorPrimaries::SMPTE240M, "SMPTE240M" },
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{ ColorPrimaries::SMPTE428, "SMPTE428" },
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{ ColorPrimaries::SMPTE431, "SMPTE431" },
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{ ColorPrimaries::SMPTE432, "SMPTE432" }
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};
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static const int num_primaries = sizeof(primary_table) / sizeof(primary_table[0]);
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class HDRGamutTest : public Screen {
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public:
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HDRGamutTest() : Screen(Vector2i(800, 600), "NanoGUI test", /* resizable */ true, /* maximized */ false,
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/* fullscreen */ false, /* depth_buffer */ true, /* stencil_buffer */ false,
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/* float_buffer */ true, /* gl_major */ 3, /* gl_minor */ 2) {
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inc_ref();
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Window *window = new Window(this, "HDR & Color gamut test");
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window->set_layout(new GroupLayout());
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m_texture = new Texture(
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Texture::PixelFormat::RGBA,
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Texture::ComponentFormat::Float32,
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Vector2i(512, 400),
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Texture::InterpolationMode::Nearest,
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Texture::InterpolationMode::Nearest
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);
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new Label(window, "Primaries");
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std::vector<std::string> primary_names;
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for (int i = 0; i < num_primaries; ++i) {
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primary_names.push_back(primary_table[i].name);
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}
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ColorPrimaries screen_primary = from_screen(this);
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int primary_index = 0;
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for (int i = 0; i < num_primaries; ++i) {
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if (primary_table[i].primary == screen_primary) {
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primary_index = i;
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break;
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}
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}
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ComboBox *primaries_cbox = new ComboBox(window, primary_names);
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primaries_cbox->set_selected_index(primary_index);
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primaries_cbox->set_callback([this](int index) {
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auto chroma_array = chroma(primary_table[index].primary);
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m_rec709_matrix = chroma_to_rec709_matrix(chroma_array);
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update_texture();
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});
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// Initialize with current selection
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auto chroma_array = chroma(primary_table[primary_index].primary);
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m_rec709_matrix = chroma_to_rec709_matrix(chroma_array);
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new Label(window, "Linear ramps (0..4), bars mark integer values. Top: LDR sRGB, bottom: HDR with chosen primaries.");
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ImageView *img = new ImageView(window);
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img->set_image(m_texture);
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img->set_size(Vector2i(512, 400));
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img->set_scale(pixel_ratio());
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perform_layout();
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window->set_position(Vector2i(5, 5));
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update_texture();
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}
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private:
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float to_srgb(float value) {
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float sign = value < 0 ? -1.0f : 1.0f;
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value = std::abs(value);
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return sign * (value < 0.0031308f ? value * 12.92f
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: 1.055f * std::pow(value, 1.0f/2.4f) - 0.055f);
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}
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void update_texture() {
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const int width = 512, height = 400;
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std::vector<float> img(width * height * 4, 0.0f);
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// Draw vertical grid lines at quarter positions
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for (int y = 0; y < height; ++y) {
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for (int x : {0, width/4, width/2, 3*width/4, width-1}) {
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float* p = &img[(y * width + x) * 4];
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p[0] = p[1] = p[2] = p[3] = 1.0f;
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}
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}
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// Draw color bars: red, green, blue, white
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const struct { int y0, y1; Vector3f srgb, primary; } bars[] = {
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{10, 90, {1, 0, 0}, m_rec709_matrix[0]},
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{110, 190, {0, 1, 0}, m_rec709_matrix[1]},
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{210, 290, {0, 0, 1}, m_rec709_matrix[2]},
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{310, 390, {1, 1, 1}, {1, 1, 1}}
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};
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for (auto& bar : bars) {
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int mid_y = (bar.y0 + bar.y1) / 2;
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for (int y = bar.y0; y < bar.y1; ++y) {
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bool is_srgb = (y < mid_y);
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for (int x = 0; x < width; ++x) {
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float ramp = x * 4.0f / (width - 1);
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float* p = &img[(y * width + x) * 4];
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for (int c = 0; c < 3; ++c) {
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float val = ramp * (is_srgb ? bar.srgb[c] : bar.primary[c]);
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p[c] = to_srgb(is_srgb ? std::min(val, 1.0f) : val);
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}
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p[3] = 1.0f;
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}
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}
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}
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m_texture->upload((uint8_t*)img.data());
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}
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private:
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ref<Texture> m_texture;
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Matrix3f m_rec709_matrix;
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};
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int main(int /* argc */, char ** /* argv */) {
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nanogui::init();
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{
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ref<HDRGamutTest> app = new HDRGamutTest();
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app->dec_ref();
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app->draw_all();
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app->set_visible(true);
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nanogui::run(RunMode::Lazy);
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}
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nanogui::shutdown();
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return 0;
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}

‎src/python/example_hdr.py‎

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import nanogui as ng
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import numpy as np
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class HDRGamutTest(ng.Screen):
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def __init__(self):
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super(HDRGamutTest, self).__init__(size=(800, 600), caption='NanoGUI test', float_buffer=True)
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window = ng.Window(self, 'HDR & Color gamut test')
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window.set_layout(ng.GroupLayout())
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self.texture = ng.Texture(
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pixel_format=ng.Texture.PixelFormat.RGBA,
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component_format=ng.Texture.ComponentFormat.Float32,
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min_interpolation_mode=ng.Texture.InterpolationMode.Nearest,
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mag_interpolation_mode=ng.Texture.InterpolationMode.Nearest,
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size=[512, 400],
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)
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ng.Label(window, "Primaries")
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primaries = sorted(ng.ituth273.ColorPrimaries, key=lambda x: x.__name__)
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primary_index = primaries.index(ng.ituth273.from_screen(self))
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primaries_cbox = ng.ComboBox(window, [p.__name__ for p in primaries])
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primaries_cbox.set_selected_index(primary_index)
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def primary_cb(index):
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p = ng.ituth273.chroma(primaries[index])
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rec709_matrix = ng.ituth273.chroma_to_rec709_matrix(p)
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self.rec709_matrix = np.from_dlpack(rec709_matrix)
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self.update_texture()
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primaries_cbox.set_callback(primary_cb)
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primary_cb(primary_index)
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ng.Label(window, "Linear ramps (0..4), bars mark integer values. Top: LDR sRGB, bottom: HDR with chosen primaries.")
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img = ng.ImageView(window)
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img.set_image(self.texture)
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img.set_size((512, 400))
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img.set_scale(self.pixel_ratio())
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self.perform_layout()
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window.set_position((5, 5))
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def create_color_bar(self, y_start, y_end, primary_color, srgb_color, max_value=4):
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img = np.zeros((y_end - y_start, 512, 4), dtype=np.float32)
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mid_y = (y_end - y_start) // 2
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ramp = np.linspace(0, max_value, 512)
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for i in range(3):
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img[:mid_y, :, i] = np.minimum(ramp * srgb_color[i], 1)
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img[mid_y:, :, i] = ramp * primary_color[i]
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img[..., 3] = 1
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return img
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def to_srgb(self, value):
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sign = np.sign(value)
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value = abs(value)
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return np.where(value < 0.0031308,
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value * 12.92,
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1.055 * value**(1.0/2.4) - 0.055) * sign
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def update_texture(self):
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"""Update texture with color bars using rec709_matrix primaries and sRGB comparison"""
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img = np.zeros((400, 512, 4), dtype=np.float32)
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# Vertical grid lines
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img[:, 0*512//4, :] = img[:, 1*512//4, :] = 1
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img[:, 2*512//4, :] = img[:, 3*512//4, :] = 1
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img[:, 511, :] = 1
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bars = [
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(10, 90, (1, 0, 0), self.rec709_matrix[:, 0]),
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(110, 190, (0, 1, 0), self.rec709_matrix[:, 1]),
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(210, 290, (0, 0, 1), self.rec709_matrix[:, 2]),
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(310, 390, (1, 1, 1), (1, 1, 1)),
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]
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for y_start, y_end, srgb, primary in bars:
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img[y_start:y_end, :, :] = self.create_color_bar(y_start, y_end, primary, srgb)
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self.texture.upload(self.to_srgb(img))
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def main():
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ng.init()
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app = HDRGamutTest()
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app.set_visible(True)
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ng.run(ng.RunMode.Lazy)
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del app
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ng.shutdown()
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if __name__ == '__main__':
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main()

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