# imgui_freetype Build font atlases using FreeType instead of stb_truetype (the default imgui's font rasterizer). <br>by @vuhdo, @mikesart, @ocornut. ### Usage 1. Get latest FreeType binaries or build yourself (under Windows you may use vcpkg with `vcpkg install freetype`). 2. Add imgui_freetype.h/cpp alongside your imgui sources. 3. Include imgui_freetype.h after imgui.h. 4. Call `ImGuiFreeType::BuildFontAtlas()` *BEFORE* calling `ImFontAtlas::GetTexDataAsRGBA32()` or `ImFontAtlas::Build()` (so normal Build() won't be called): ```cpp // See ImGuiFreeType::RasterizationFlags unsigned int flags = ImGuiFreeType::NoHinting; ImGuiFreeType::BuildFontAtlas(io.Fonts, flags); io.Fonts->GetTexDataAsRGBA32(&pixels, &width, &height); ``` ### Gamma Correct Blending FreeType assumes blending in linear space rather than gamma space. See FreeType note for [FT_Render_Glyph](https://www.freetype.org/freetype2/docs/reference/ft2-base_interface.html#FT_Render_Glyph). For correct results you need to be using sRGB and convert to linear space in the pixel shader output. The default imgui styles will be impacted by this change (alpha values will need tweaking). ### Test code Usage ```cpp #include "misc/freetype/imgui_freetype.h" #include "misc/freetype/imgui_freetype.cpp" // Load various small fonts ImGuiIO& io = ImGui::GetIO(); io.Fonts->AddFontFromFileTTF("../../misc/fonts/Roboto-Medium.ttf", 13.0f); io.Fonts->AddFontFromFileTTF("../../misc/fonts/Cousine-Regular.ttf", 13.0f); io.Fonts->AddFontDefault(); FreeTypeTest freetype_test; // Main Loop while (true) { if (freetype_test.UpdateRebuild()) { // REUPLOAD FONT TEXTURE TO GPU // e.g ImGui_ImplOpenGL3_DestroyDeviceObjects() + ImGui_ImplOpenGL3_CreateDeviceObjects() } ImGui::NewFrame(); freetype_test.ShowFreetypeOptionsWindow(); ... } ``` ### Test code ```cpp #include "misc/freetype/imgui_freetype.h" #include "misc/freetype/imgui_freetype.cpp" struct FreeTypeTest { enum FontBuildMode { FontBuildMode_FreeType, FontBuildMode_Stb }; FontBuildMode BuildMode; bool WantRebuild; float FontsMultiply; int FontsPadding; unsigned int FontsFlags; FreeTypeTest() { BuildMode = FontBuildMode_FreeType; WantRebuild = true; FontsMultiply = 1.0f; FontsPadding = 1; FontsFlags = 0; } // Call _BEFORE_ NewFrame() bool UpdateRebuild() { if (!WantRebuild) return false; ImGuiIO& io = ImGui::GetIO(); for (int n = 0; n < io.Fonts->Fonts.Size; n++) { ImFontConfig* font_config = (ImFontConfig*)io.Fonts->Fonts[n]->ConfigData; io.Fonts->TexGlyphPadding = FontsPadding; font_config->RasterizerMultiply = FontsMultiply; font_config->RasterizerFlags = (BuildMode == FontBuildMode_FreeType) ? FontsFlags : 0x00; } if (BuildMode == FontBuildMode_FreeType) ImGuiFreeType::BuildFontAtlas(io.Fonts, FontsFlags); else if (BuildMode == FontBuildMode_Stb) io.Fonts->Build(); WantRebuild = false; return true; } // Call to draw interface void ShowFreetypeOptionsWindow() { ImGui::Begin("FreeType Options"); ImGui::ShowFontSelector("Fonts"); WantRebuild |= ImGui::RadioButton("FreeType", (int*)&BuildMode, FontBuildMode_FreeType); ImGui::SameLine(); WantRebuild |= ImGui::RadioButton("Stb (Default)", (int*)&BuildMode, FontBuildMode_Stb); WantRebuild |= ImGui::DragFloat("Multiply", &FontsMultiply, 0.001f, 0.0f, 2.0f); WantRebuild |= ImGui::DragInt("Padding", &FontsPadding, 0.1f, 0, 16); if (BuildMode == FontBuildMode_FreeType) { WantRebuild |= ImGui::CheckboxFlags("NoHinting", &FontsFlags, ImGuiFreeType::NoHinting); WantRebuild |= ImGui::CheckboxFlags("NoAutoHint", &FontsFlags, ImGuiFreeType::NoAutoHint); WantRebuild |= ImGui::CheckboxFlags("ForceAutoHint", &FontsFlags, ImGuiFreeType::ForceAutoHint); WantRebuild |= ImGui::CheckboxFlags("LightHinting", &FontsFlags, ImGuiFreeType::LightHinting); WantRebuild |= ImGui::CheckboxFlags("MonoHinting", &FontsFlags, ImGuiFreeType::MonoHinting); WantRebuild |= ImGui::CheckboxFlags("Bold", &FontsFlags, ImGuiFreeType::Bold); WantRebuild |= ImGui::CheckboxFlags("Oblique", &FontsFlags, ImGuiFreeType::Oblique); } ImGui::End(); } }; ``` ### Known issues - `cfg.OversampleH`, `OversampleV` are ignored (but perhaps not so necessary with this rasterizer).