zebra stripes in gles

Author: wkjarosz

assets/shaders/image-shader_frag.glsl

@@ -166,23 +166,25 @@ float sample_channel(sampler2D sampler, vec2 uv, bool within_image)
 
 void main()
 {
+    vec2 pixel      = vec2(gl_FragCoord.x, -gl_FragCoord.y);
     vec4 background = vec4(bg_color.rgb, 1.0);
     if (bg_mode == BG_BLACK)
         background.rgb = vec3(0.0);
     else if (bg_mode == BG_WHITE)
         background.rgb = vec3(1.0);
     else if (bg_mode == BG_DARK_CHECKER || bg_mode == BG_LIGHT_CHECKER)
     {
-        float dark_gray  = (bg_mode == BG_DARK_CHECKER) ? 0.1 : 0.5;
-        float light_gray = (bg_mode == BG_DARK_CHECKER) ? 0.2 : 0.55;
-        float checkerboard =
-            mod(floor(gl_FragCoord.x / 8.0) + floor(gl_FragCoord.y / 8.0), 2.0) == 0.0 ? dark_gray : light_gray;
-        background.rgb = sRGBToLinear(vec3(checkerboard));
+        float dark_gray    = (bg_mode == BG_DARK_CHECKER) ? 0.1 : 0.5;
+        float light_gray   = (bg_mode == BG_DARK_CHECKER) ? 0.2 : 0.55;
+        float checkerboard = mod(floor(pixel.x / 8.0) + floor(pixel.y / 8.0), 2.0) == 0.0 ? dark_gray : light_gray;
+        background.rgb     = sRGBToLinear(vec3(checkerboard));
     }
 
+    float zebra1 = (mod(float(int(floor((pixel.x + pixel.y - 30.0 * time) / 8.0))), 2.0) == 0.0) ? 0.0 : 1.0;
+    float zebra2 = (mod(float(int(floor((pixel.x - pixel.y - 30.0 * time) / 8.0))), 2.0) == 0.0) ? 0.0 : 1.0;
+
     bool in_img = primary_uv.x < 1.0 && primary_uv.y < 1.0 && primary_uv.x > 0.0 && primary_uv.y > 0.0;
-    bool in_ref =
-        secondary_uv.x < 1.0 && secondary_uv.y < 1.0 && secondary_uv.x > 0.0 && secondary_uv.y > 0.0 && has_reference;
+    bool in_ref = secondary_uv.x < 1.0 && secondary_uv.y < 1.0 && secondary_uv.x > 0.0 && secondary_uv.y > 0.0;
 
     if (!in_img && !(in_ref && has_reference))
     {
@@ -214,8 +216,17 @@ void main()
         value = blend(value, reference_val);
     }
 
-    vec4 foreground = choose_channel(value) * vec4(vec3(gain), 1.0);
-    vec4 blended    = dither(linearToSRGB(tonemap(foreground) + background * (1.0 - foreground.a)));
-    blended         = clamp(blended, clamp_to_LDR ? 0.0 : -64.0, clamp_to_LDR ? 1.0 : 64.0);
-    frag_color      = vec4(blended.rgb, 1.0);
+    vec4  foreground = choose_channel(value) * vec4(vec3(gain), 1.0);
+    vec4  tonemapped = tonemap(foreground) + background * (1.0 - foreground.a);
+    bvec3 clipped    = greaterThan(foreground.rgb, clip_range.yyy);
+    bvec3 crushed    = lessThan(foreground.rgb, clip_range.xxx);
+    vec4  blended    = linearToSRGB(tonemapped);
+    vec4  dithered   = dither(blended);
+    dithered         = clamp(dithered, clamp_to_LDR ? 0.0 : -64.0, clamp_to_LDR ? 1.0 : 64.0);
+    if (draw_clip_warnings)
+    {
+        dithered.rgb = mix(dithered.rgb, vec3(zebra1), clipped);
+        dithered.rgb = mix(dithered.rgb, vec3(zebra2), crushed);
+    }
+    frag_color = vec4(dithered.rgb, 1.0);
 }

assets/shaders/image-shader_frag.metal

@@ -194,7 +194,7 @@ fragment float4 fragment_main(VertexOut vert [[stage_in]],
     float zebra2 = (fmod(float(int(floor((vert.position.x - vert.position.y - 30.0*time) / 8.0))), 2.0) == 0.0) ? 0.0 : 1.0;
 
     bool in_img = all(vert.primary_uv < 1.0) and all(vert.primary_uv > 0.0);
-    bool in_ref = all(vert.secondary_uv < 1.0) and all(vert.secondary_uv > 0.0);// and has_reference;
+    bool in_ref = all(vert.secondary_uv < 1.0) and all(vert.secondary_uv > 0.0);
 
     if (!in_img and !(in_ref and has_reference))
         return linearToSRGB(background);

src/app.cpp

@@ -275,7 +275,7 @@ HDRViewApp::HDRViewApp(std::optional<float> force_exposure, std::optional<float>
     HelloImGui::DockableWindow advanced_settings_window;
     advanced_settings_window.label             = "Advanced settings";
     advanced_settings_window.dockSpaceName     = "RightSpace";
-    advanced_settings_window.isVisible         = true;
+    advanced_settings_window.isVisible         = false;
     advanced_settings_window.rememberIsVisible = true;
     advanced_settings_window.GuiFunction       = [this]
     {
@@ -285,8 +285,8 @@ HDRViewApp::HDRViewApp(std::optional<float> force_exposure, std::optional<float>
             ImGui::SameLine();
             ImGui::PushItemWidth(-5 * HelloImGui::EmSize());
             ImGui::BeginDisabled(!m_draw_clip_warnings);
-            ImGui::DragFloatRange2("Clip warning", &m_clip_range.min.x, &m_clip_range.max.x, 0.01f, 0.f, 0.f,
-                                   "min: %.1f", "max: %.1f");
+            ImGui::DragFloatRange2("Clip warning", &m_clip_range.x, &m_clip_range.y, 0.01f, 0.f, 0.f, "min: %.1f",
+                                   "max: %.1f");
             ImGui::EndDisabled();
             ImGui::PopItemWidth();
             // ImGui::TreePop();
@@ -1073,6 +1073,8 @@ void HDRViewApp::load_settings()
         m_dither               = j.value<bool>("dither", m_dither);
         g_file_list_mode       = j.value<int>("file list mode", g_file_list_mode);
         g_short_names          = j.value<bool>("short names", g_short_names);
+        m_draw_clip_warnings   = j.value<bool>("draw clip warnings", m_draw_clip_warnings);
+        m_clip_range           = j.value<float2>("clip range", m_clip_range);
     }
     catch (json::exception &e)
     {
@@ -1102,6 +1104,8 @@ void HDRViewApp::save_settings()
     j["verbosity"]               = spdlog::get_level();
     j["file list mode"]          = g_file_list_mode;
     j["short names"]             = g_short_names;
+    j["draw clip warnings"]      = m_draw_clip_warnings;
+    j["clip range"]              = m_clip_range;
     HelloImGui::SaveUserPref("UserSettings", j.dump(4));
 }
 
@@ -2622,7 +2626,7 @@ void HDRViewApp::draw_image() const
 
         m_shader->set_uniform("time", (float)ImGui::GetTime());
         m_shader->set_uniform("draw_clip_warnings", m_draw_clip_warnings);
-        m_shader->set_uniform("clip_range", float2{m_clip_range.min.x, m_clip_range.max.x});
+        m_shader->set_uniform("clip_range", m_clip_range);
         m_shader->set_uniform("randomness", randomness);
         m_shader->set_uniform("gain", powf(2.0f, m_exposure_live));
         m_shader->set_uniform("gamma", m_gamma_live);

src/app.h

@@ -222,9 +222,9 @@ class HDRViewApp
     AxisScale_ m_x_scale = AxisScale_Asinh, m_y_scale = AxisScale_Linear;
     bool       m_clamp_to_LDR = false, m_dither = true, m_draw_grid = true, m_draw_pixel_info = true,
          m_draw_watched_pixels = true, m_draw_data_window = true, m_draw_display_window = true,
-         m_draw_clip_warnings = true;
-    Box1f m_clip_range{0.f, 1.f};
-    Box2i m_roi = Box2i{int2{0}}, m_roi_live = Box2i{int2{0}};
+         m_draw_clip_warnings = false;
+    float2 m_clip_range{0.f, 1.f}; ///< Values outside this range will have zebra stripes if m_draw_clip_warnings = true
+    Box2i  m_roi{int2{0}}, m_roi_live{int2{0}};
 
     // Image display parameters.
     float m_zoom_sensitivity = 1.0717734625f;