Improve text redering and do all color operation in gamma space

CHANGELOG.md

@@ -6,6 +6,10 @@ NOTE: [`epaint`](crates/epaint/CHANGELOG.md), [`eframe`](crates/eframe/CHANGELOG
 
 ## Unreleased
 * ⚠️ BREAKING: Fix text being too small ([#2069](https://github.com/emilk/egui/pull/2069)).
+* ⚠️ BREAKING: egui now expects integrations to do all color blending in gamma space ([#2071](https://github.com/emilk/egui/pull/2071)).
+
+### Fixed 🐛
+* Improved text rendering ([#2071](https://github.com/emilk/egui/pull/2071)).
 
 
 ## 0.19.0 - 2022-08-20

crates/eframe/src/native/run.rs

@@ -338,7 +338,7 @@ mod glow_integration {
  .with_hardware_acceleration(hardware_acceleration)
  .with_depth_buffer(native_options.depth_buffer)
  .with_multisampling(native_options.multisampling)
- .with_srgb(true)
+ .with_srgb(false)
  .with_stencil_buffer(native_options.stencil_buffer)
  .with_vsync(native_options.vsync)
  .build_windowed(window_builder, event_loop)
@@ -365,7 +365,7 @@ mod glow_integration {
  let gl = Arc::new(gl);
 
  let painter =
- egui_glow::Painter::new(gl.clone(), None, "", self.native_options.shader_version)
+ egui_glow::Painter::new(gl.clone(), "", self.native_options.shader_version)
  .unwrap_or_else(|error| panic!("some OpenGL error occurred {}\n", error));
 
  let system_theme = self.native_options.system_theme();

crates/eframe/src/web/web_glow_painter.rs

@@ -22,8 +22,7 @@ impl WebPainter {
  let (gl, shader_prefix) = init_glow_context_from_canvas(&canvas, options)?;
  let gl = std::sync::Arc::new(gl);
 
- let dimension = [canvas.width() as i32, canvas.height() as i32];
- let painter = egui_glow::Painter::new(gl, Some(dimension), shader_prefix, None)
+ let painter = egui_glow::Painter::new(gl, shader_prefix, None)
  .map_err(|error| format!("Error starting glow painter: {}", error))?;
 
  Ok(Self {

crates/egui-wgpu/CHANGELOG.md

@@ -3,10 +3,10 @@ All notable changes to the `egui-wgpu` integration will be noted in this file.
 
 
 ## Unreleased
-* Rename `RenderPass` to `Renderer`
-* Rename `RenderPass::execute` to `RenderPass::render`
-* Rename `RenderPass::execute_with_renderpass` to `Renderer::render_onto_renderpass`
-* Reexport `Renderer`
+* Renamed `RenderPass` to `Renderer`.
+* Renamed `RenderPass::execute` to `RenderPass::render`.
+* Renamed `RenderPass::execute_with_renderpass` to `Renderer::render_onto_renderpass`.
+* Reexported `Renderer`.
 
 
 ## 0.19.0 - 2022-08-20

crates/egui-wgpu/src/egui.wgsl

@@ -2,7 +2,7 @@
 
 struct VertexOutput {
  @location(0) tex_coord: vec2<f32>,
- @location(1) color: vec4<f32>,
+ @location(1) color: vec4<f32>, // gamma 0-1
  @builtin(position) position: vec4<f32>,
 };
 
@@ -14,22 +14,35 @@ struct Locals {
 };
 @group(0) @binding(0) var<uniform> r_locals: Locals;
 
-// 0-1 from 0-255
-fn linear_from_srgb(srgb: vec3<f32>) -> vec3<f32> {
- let cutoff = srgb < vec3<f32>(10.31475);
- let lower = srgb / vec3<f32>(3294.6);
- let higher = pow((srgb + vec3<f32>(14.025)) / vec3<f32>(269.025), vec3<f32>(2.4));
+// 0-1 linear from  0-1 sRGB gamma
+fn linear_from_gamma_rgb(srgb: vec3<f32>) -> vec3<f32> {
+ let cutoff = srgb < vec3<f32>(0.04045);
+ let lower = srgb / vec3<f32>(12.92);
+ let higher = pow((srgb + vec3<f32>(0.055)) / vec3<f32>(1.055), vec3<f32>(2.4));
  return select(higher, lower, cutoff);
 }
 
-// [u8; 4] SRGB as u32 -> [r, g, b, a]
+// 0-1 sRGB gamma from 0-1 linear
+fn gamma_from_linear_rgb(rgb: vec3<f32>) -> vec3<f32> {
+ let cutoff = rgb < vec3<f32>(0.0031308);
+ let lower = rgb * vec3<f32>(12.92);
+ let higher = vec3<f32>(1.055) * pow(rgb, vec3<f32>(1.0 / 2.4)) - vec3<f32>(0.055);
+ return select(higher, lower, cutoff);
+}
+
+// 0-1 sRGBA gamma from 0-1 linear
+fn gamma_from_linear_rgba(linear_rgba: vec4<f32>) -> vec4<f32> {
+ return vec4<f32>(gamma_from_linear_rgb(linear_rgba.rgb), linear_rgba.a);
+}
+
+// [u8; 4] SRGB as u32 -> [r, g, b, a] in 0.-1
 fn unpack_color(color: u32) -> vec4<f32> {
  return vec4<f32>(
  f32(color & 255u),
  f32((color >> 8u) & 255u),
  f32((color >> 16u) & 255u),
  f32((color >> 24u) & 255u),
- );
+ ) / 255.0;
 }
 
 fn position_from_screen(screen_pos: vec2<f32>) -> vec4<f32> {
@@ -49,22 +62,7 @@ fn vs_main(
 ) -> VertexOutput {
  var out: VertexOutput;
  out.tex_coord = a_tex_coord;
- let color = unpack_color(a_color);
- out.color = vec4<f32>(linear_from_srgb(color.rgb), color.a / 255.0);
- out.position = position_from_screen(a_pos);
- return out;
-}
-
-@vertex
-fn vs_conv_main(
- @location(0) a_pos: vec2<f32>,
- @location(1) a_tex_coord: vec2<f32>,
- @location(2) a_color: u32,
-) -> VertexOutput {
- var out: VertexOutput;
- out.tex_coord = a_tex_coord;
- let color = unpack_color(a_color);
- out.color = vec4<f32>(color.rgba / 255.0);
+ out.color = unpack_color(a_color);
  out.position = position_from_screen(a_pos);
  return out;
 }
@@ -75,6 +73,19 @@ fn vs_conv_main(
 @group(1) @binding(1) var r_tex_sampler: sampler;
 
 @fragment
-fn fs_main(in: VertexOutput) -> @location(0) vec4<f32> {
- return in.color * textureSample(r_tex_color, r_tex_sampler, in.tex_coord);
+fn fs_main_linear_framebuffer(in: VertexOutput) -> @location(0) vec4<f32> {
+ // We always have an sRGB aware texture at the moment.
+ let tex_linear = textureSample(r_tex_color, r_tex_sampler, in.tex_coord);
+ let tex_gamma = gamma_from_linear_rgba(tex_linear);
+ let out_color_gamma = in.color * tex_gamma;
+ return vec4<f32>(linear_from_gamma_rgb(out_color_gamma.rgb), out_color_gamma.a);
+}
+
+@fragment
+fn fs_main_gamma_framebuffer(in: VertexOutput) -> @location(0) vec4<f32> {
+ // We always have an sRGB aware texture at the moment.
+ let tex_linear = textureSample(r_tex_color, r_tex_sampler, in.tex_coord);
+ let tex_gamma = gamma_from_linear_rgba(tex_linear);
+ let out_color_gamma = in.color * tex_gamma;
+ return out_color_gamma;
 }

crates/egui-wgpu/src/renderer.rs

@@ -140,7 +140,8 @@ pub struct Renderer {
 impl Renderer {
  /// Creates a renderer for a egui UI.
  ///
- /// If the format passed is not a *Srgb format, the shader will automatically convert to `sRGB` colors in the shader.
+ /// `output_format` should preferably be [`wgpu::TextureFormat::Rgba8Unorm`] or
+ /// [`wgpu::TextureFormat::Bgra8Unorm`], i.e. in gamma-space.
  pub fn new(
  device: &wgpu::Device,
  output_format: wgpu::TextureFormat,
@@ -235,11 +236,7 @@ impl Renderer {
  label: Some("egui_pipeline"),
  layout: Some(&pipeline_layout),
  vertex: wgpu::VertexState {
- entry_point: if output_format.describe().srgb {
- "vs_main"
- } else {
- "vs_conv_main"
- },
+ entry_point: "vs_main",
  module: &module,
  buffers: &[wgpu::VertexBufferLayout {
  array_stride: 5 * 4,
@@ -268,7 +265,12 @@ impl Renderer {
 
  fragment: Some(wgpu::FragmentState {
  module: &module,
- entry_point: "fs_main",
+ entry_point: if output_format.describe().srgb {
+ tracing::warn!("Detected a linear (sRGBA aware) framebuffer {:?}. egui prefers Rgba8Unorm or Bgra8Unorm", output_format);
+ "fs_main_linear_framebuffer"
+ } else {
+ "fs_main_gamma_framebuffer" // this is what we prefer
+ },
  targets: &[Some(wgpu::ColorTargetState {
  format: output_format,
  blend: Some(wgpu::BlendState {
@@ -518,7 +520,7 @@ impl Renderer {
  image.pixels.len(),
  "Mismatch between texture size and texel count"
  );
- Cow::Owned(image.srgba_pixels(1.0).collect::<Vec<_>>())
+ Cow::Owned(image.srgba_pixels(None).collect::<Vec<_>>())
  }
  };
  let data_bytes: &[u8] = bytemuck::cast_slice(data_color32.as_slice());
@@ -564,7 +566,7 @@ impl Renderer {
  mip_level_count: 1,
  sample_count: 1,
  dimension: wgpu::TextureDimension::D2,
- format: wgpu::TextureFormat::Rgba8UnormSrgb,
+ format: wgpu::TextureFormat::Rgba8UnormSrgb, // TODO(emilk): handle WebGL1 where this is not always supported!
  usage: wgpu::TextureUsages::TEXTURE_BINDING | wgpu::TextureUsages::COPY_DST,
  });
  let filter = match image_delta.filter {

crates/egui-wgpu/src/winit.rs

@@ -117,7 +117,9 @@ impl<'a> Painter<'a> {
 
  if self.render_state.is_none() {
  let adapter = self.adapter.as_ref().unwrap();
- let swapchain_format = surface.get_supported_formats(adapter)[0];
+
+ let swapchain_format =
+ select_framebuffer_format(&surface.get_supported_formats(adapter));
 
  let rs = pollster::block_on(self.init_render_state(adapter, swapchain_format));
  self.render_state = Some(rs);
@@ -322,3 +324,15 @@ impl<'a> Painter<'a> {
  // TODO(emilk): something here?
  }
 }
+
+fn select_framebuffer_format(formats: &[wgpu::TextureFormat]) -> wgpu::TextureFormat {
+ for &format in formats {
+ if matches!(
+ format,
+ wgpu::TextureFormat::Rgba8Unorm | wgpu::TextureFormat::Bgra8Unorm
+ ) {
+ return format;
+ }
+ }
+ formats[0] // take the first
+}