Automatically determine image/tensor color mapping & need for srgb decoding (#2342)

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### What

Fixes #2274 
* #2274 

Will need to be further worked on via:
* #2341


Introduces 3 new things actually:
* finite range, determined if the range of a tensor was in fact not
finite
* heuristic for color mapping range
* heuristic for srgb
   * ⚠️ does this break things?


Range & sRGB:

This
```
import rerun as rr
import numpy as np
import matplotlib.pyplot as plt

rr.init("image color", spawn=True)
img = np.random.random((300, 300, 3)) * 0.2
rr.log_image("image", img)
print(img.min(), img.max())  # to check they are in range [0,1]

plt.imshow(img)
plt.show()
```
Gives now the expected image:

![image](https://github.com/rerun-io/rerun/assets/1220815/9fcda125-f762-4fd4-ae24-ce6dcaaa496a)


When setting a pixel to inf, we show the "finite range" as well, and
behave correctly:
<img width="1026" alt="image"
src="https://github.com/rerun-io/rerun/assets/1220815/7d3037e8-f562-4b6c-8f08-ec4f5627c21a">


### Checklist
* [x] I have read and agree to [Contributor
Guide](https://github.com/rerun-io/rerun/blob/main/CONTRIBUTING.md) and
the [Code of
Conduct](https://github.com/rerun-io/rerun/blob/main/CODE_OF_CONDUCT.md)
* [x] I've included a screenshot or gif (if applicable)

<!-- This line will get updated when the PR build summary job finishes.
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PR Build Summary: https://build.rerun.io/pr/2342

<!-- pr-link-docs:start -->
Docs preview: https://rerun.io/preview/93697e6/docs
Examples preview: https://rerun.io/preview/93697e6/examples
<!-- pr-link-docs:end -->

Author: Wumpf

crates/re_components/src/tensor.rs

@@ -565,7 +565,7 @@ impl re_log_types::Component for Tensor {
     }
 }
 
-#[derive(thiserror::Error, Debug, PartialEq)]
+#[derive(thiserror::Error, Debug, PartialEq, Clone)]
 pub enum TensorCastError {
     #[error("ndarray type mismatch with tensor storage")]
     TypeMismatch,

crates/re_data_ui/src/image.rs

@@ -278,7 +278,10 @@ pub fn tensor_summary_ui_grid_contents(
         }
     }
 
-    let TensorStats { range } = tensor_stats;
+    let TensorStats {
+        range,
+        finite_range,
+    } = tensor_stats;
 
     if let Some((min, max)) = range {
         ui.label("Data range")
@@ -290,6 +293,17 @@ pub fn tensor_summary_ui_grid_contents(
         ));
         ui.end_row();
     }
+    // Show finite range only if it is different from the actual range.
+    if let (true, Some((min, max))) = (range != finite_range, finite_range) {
+        ui.label("Finite data range")
+            .on_hover_text("The finite values (ignoring all NaN & -Inf/+Inf) of the tensor range within these bounds.");
+        ui.monospace(format!(
+            "[{} - {}]",
+            re_format::format_f64(*min),
+            re_format::format_f64(*max)
+        ));
+        ui.end_row();
+    }
 }
 
 pub fn tensor_summary_ui(

crates/re_renderer/shader/rectangle.wgsl

@@ -53,6 +53,9 @@ struct UniformBuffer {
 
     /// Boolean: decode 0-1 sRGB gamma to linear space before filtering?
     decode_srgb: u32,
+
+    /// Boolean: multiply RGB with alpha before filtering
+    multiply_rgb_with_alpha: u32,
 };
 
 @group(1) @binding(0)

crates/re_renderer/shader/rectangle_fs.wgsl

@@ -14,78 +14,85 @@ fn tex_filter(pixel_coord: Vec2) -> u32 {
     }
 }
 
-fn decode_color(rgba_arg: Vec4) -> Vec4 {
-    var rgba = rgba_arg;
+fn normalize_range(sampled_value: Vec4) -> Vec4 {
+    let range = rect_info.range_min_max;
+    return (sampled_value - range.x) / (range.y - range.x);
+}
+
+fn decode_color(sampled_value: Vec4) -> Vec4 {
+    // Normalize the value first, otherwise premultiplying alpha and linear space conversion won't make sense.
+    var rgba = normalize_range(sampled_value);
 
-    // Convert to linear space:
+    // Convert to linear space
     if rect_info.decode_srgb != 0u {
-        rgba = linear_from_srgba(rgba);
+        if all(0.0 <= rgba.rgb) && all(rgba.rgb <= 1.0) {
+            rgba = linear_from_srgba(rgba);
+        } else {
+            rgba = ERROR_RGBA; // out of range
+        }
     }
 
-    // Premultiply alpha:
-    rgba = vec4(rgba.xyz * rgba.a, rgba.a);
+    // Premultiply alpha.
+    if rect_info.multiply_rgb_with_alpha != 0u {
+        rgba = vec4(rgba.xyz * rgba.a, rgba.a);
+    }
 
     return rgba;
 }
 
+fn filter_bilinear(coord: Vec2, v00: Vec4, v01: Vec4, v10: Vec4, v11: Vec4) -> Vec4 {
+    let top = mix(v00, v10, fract(coord.x - 0.5));
+    let bottom = mix(v01, v11, fract(coord.x - 0.5));
+    return mix(top, bottom, fract(coord.y - 0.5));
+}
+
 @fragment
 fn fs_main(in: VertexOut) -> @location(0) Vec4 {
     // Sample the main texture:
-    var sampled_value: Vec4;
+    var normalized_value: Vec4;
     if rect_info.sample_type == SAMPLE_TYPE_FLOAT {
         let coord = in.texcoord * Vec2(textureDimensions(texture_float).xy);
         if tex_filter(coord) == FILTER_NEAREST {
             // nearest
-            sampled_value = decode_color(textureLoad(texture_float, IVec2(coord), 0));
+            normalized_value = decode_color(textureLoad(texture_float, IVec2(coord), 0));
         } else {
             // bilinear
             let v00 = decode_color(textureLoad(texture_float, IVec2(coord + vec2(-0.5, -0.5)), 0));
             let v01 = decode_color(textureLoad(texture_float, IVec2(coord + vec2(-0.5,  0.5)), 0));
             let v10 = decode_color(textureLoad(texture_float, IVec2(coord + vec2( 0.5, -0.5)), 0));
             let v11 = decode_color(textureLoad(texture_float, IVec2(coord + vec2( 0.5,  0.5)), 0));
-            let top = mix(v00, v10, fract(coord.x - 0.5));
-            let bottom = mix(v01, v11, fract(coord.x - 0.5));
-            sampled_value = mix(top, bottom, fract(coord.y - 0.5));
+            normalized_value = filter_bilinear(coord, v00, v01, v10, v11);
         }
     } else if rect_info.sample_type == SAMPLE_TYPE_SINT {
         let coord = in.texcoord * Vec2(textureDimensions(texture_sint).xy);
         if tex_filter(coord) == FILTER_NEAREST {
             // nearest
-            sampled_value = Vec4(textureLoad(texture_sint, IVec2(coord), 0));
+            normalized_value = decode_color(Vec4(textureLoad(texture_sint, IVec2(coord), 0)));
         } else {
             // bilinear
-            let v00 = Vec4(textureLoad(texture_sint, IVec2(coord + vec2(-0.5, -0.5)), 0));
-            let v01 = Vec4(textureLoad(texture_sint, IVec2(coord + vec2(-0.5,  0.5)), 0));
-            let v10 = Vec4(textureLoad(texture_sint, IVec2(coord + vec2( 0.5, -0.5)), 0));
-            let v11 = Vec4(textureLoad(texture_sint, IVec2(coord + vec2( 0.5,  0.5)), 0));
-            let top = mix(v00, v10, fract(coord.x - 0.5));
-            let bottom = mix(v01, v11, fract(coord.x - 0.5));
-            sampled_value = mix(top, bottom, fract(coord.y - 0.5));
+            let v00 = decode_color(Vec4(textureLoad(texture_sint, IVec2(coord + vec2(-0.5, -0.5)), 0)));
+            let v01 = decode_color(Vec4(textureLoad(texture_sint, IVec2(coord + vec2(-0.5,  0.5)), 0)));
+            let v10 = decode_color(Vec4(textureLoad(texture_sint, IVec2(coord + vec2( 0.5, -0.5)), 0)));
+            let v11 = decode_color(Vec4(textureLoad(texture_sint, IVec2(coord + vec2( 0.5,  0.5)), 0)));
+            normalized_value = filter_bilinear(coord, v00, v01, v10, v11);
         }
     } else if rect_info.sample_type == SAMPLE_TYPE_UINT {
-        // TODO(emilk): support premultiplying alpha on this path. Requires knowing the alpha range (255, 65535, …).
         let coord = in.texcoord * Vec2(textureDimensions(texture_uint).xy);
         if tex_filter(coord) == FILTER_NEAREST {
             // nearest
-            sampled_value = Vec4(textureLoad(texture_uint, IVec2(coord), 0));
+            normalized_value = decode_color(Vec4(textureLoad(texture_uint, IVec2(coord), 0)));
         } else {
             // bilinear
-            let v00 = Vec4(textureLoad(texture_uint, IVec2(coord + vec2(-0.5, -0.5)), 0));
-            let v01 = Vec4(textureLoad(texture_uint, IVec2(coord + vec2(-0.5,  0.5)), 0));
-            let v10 = Vec4(textureLoad(texture_uint, IVec2(coord + vec2( 0.5, -0.5)), 0));
-            let v11 = Vec4(textureLoad(texture_uint, IVec2(coord + vec2( 0.5,  0.5)), 0));
-            let top = mix(v00, v10, fract(coord.x - 0.5));
-            let bottom = mix(v01, v11, fract(coord.x - 0.5));
-            sampled_value = mix(top, bottom, fract(coord.y - 0.5));
+            let v00 = decode_color(Vec4(textureLoad(texture_uint, IVec2(coord + vec2(-0.5, -0.5)), 0)));
+            let v01 = decode_color(Vec4(textureLoad(texture_uint, IVec2(coord + vec2(-0.5,  0.5)), 0)));
+            let v10 = decode_color(Vec4(textureLoad(texture_uint, IVec2(coord + vec2( 0.5, -0.5)), 0)));
+            let v11 = decode_color(Vec4(textureLoad(texture_uint, IVec2(coord + vec2( 0.5,  0.5)), 0)));
+            normalized_value = filter_bilinear(coord, v00, v01, v10, v11);
         }
     } else {
         return ERROR_RGBA; // unknown sample type
     }
 
-    // Normalize the sample:
-    let range = rect_info.range_min_max;
-    var normalized_value: Vec4 = (sampled_value - range.x) / (range.y - range.x);
-
     // Apply gamma:
     normalized_value = vec4(pow(normalized_value.rgb, vec3(rect_info.gamma)), normalized_value.a);
 

crates/re_renderer/src/renderer/rectangles.rs

@@ -53,14 +53,23 @@ pub enum TextureFilterMin {
 pub struct ColormappedTexture {
     pub texture: GpuTexture2D,
 
+    /// Min/max range of the values in the texture.
+    ///
+    /// Used to normalize the input values (squash them to the 0-1 range).
+    /// The normalization is applied before sRGB gamma decoding and alpha pre-multiplication
+    /// (this transformation is also applied to alpha!).
+    pub range: [f32; 2],
+
     /// Decode 0-1 sRGB gamma values to linear space before filtering?
     ///
     /// Only applies to [`wgpu::TextureFormat::Rgba8Unorm`] and float textures.
     pub decode_srgb: bool,
 
-    /// Min/max range of the values in the texture.
-    /// Used to normalize the input values (squash them to the 0-1 range).
-    pub range: [f32; 2],
+    /// Multiply color channels with the alpha channel before filtering?
+    ///
+    /// Set this to false for textures that don't have an alpha channel or are already pre-multiplied.
+    /// Applied after range normalization and srgb decoding, before filtering.
+    pub multiply_rgb_with_alpha: bool,
 
     /// Raise the normalized values to this power (before any color mapping).
     /// Acts like an inverse brightness.
@@ -102,6 +111,7 @@ impl ColormappedTexture {
             decode_srgb,
             range: [0.0, 1.0],
             gamma: 1.0,
+            multiply_rgb_with_alpha: true,
             color_mapper: None,
         }
     }
@@ -224,7 +234,8 @@ mod gpu_data {
         magnification_filter: u32,
 
         decode_srgb: u32,
-        _row_padding: [u32; 3],
+        multiply_rgb_with_alpha: u32,
+        _row_padding: [u32; 2],
 
         _end_padding: [wgpu_buffer_types::PaddingRow; 16 - 7],
     }
@@ -251,6 +262,7 @@ mod gpu_data {
                 range,
                 gamma,
                 color_mapper,
+                multiply_rgb_with_alpha,
             } = colormapped_texture;
 
             let super::RectangleOptions {
@@ -322,6 +334,7 @@ mod gpu_data {
                 minification_filter,
                 magnification_filter,
                 decode_srgb: *decode_srgb as _,
+                multiply_rgb_with_alpha: *multiply_rgb_with_alpha as _,
                 _row_padding: Default::default(),
                 _end_padding: Default::default(),
             })

crates/re_space_view_tensor/src/space_view_class.rs

@@ -429,8 +429,9 @@ fn paint_colormap_gradient(
 
     let colormapped_texture = re_renderer::renderer::ColormappedTexture {
         texture: horizontal_gradient,
-        decode_srgb: false,
         range: [0.0, 1.0],
+        decode_srgb: false,
+        multiply_rgb_with_alpha: false,
         gamma: 1.0,
         color_mapper: Some(re_renderer::renderer::ColorMapper::Function(colormap)),
     };

crates/re_space_view_tensor/src/tensor_slice_to_gpu.rs

@@ -4,7 +4,7 @@ use re_renderer::{
     resource_managers::{GpuTexture2D, Texture2DCreationDesc, TextureManager2DError},
 };
 use re_viewer_context::{
-    gpu_bridge::{self, range, RangeError},
+    gpu_bridge::{self, tensor_data_range_heuristic, RangeError},
     TensorStats,
 };
 
@@ -30,16 +30,17 @@ pub fn colormapped_texture(
 ) -> Result<ColormappedTexture, TextureManager2DError<TensorUploadError>> {
     re_tracing::profile_function!();
 
-    let range =
-        range(tensor_stats).map_err(|err| TextureManager2DError::DataCreation(err.into()))?;
+    let range = tensor_data_range_heuristic(tensor_stats, tensor.dtype())
+        .map_err(|err| TextureManager2DError::DataCreation(err.into()))?;
     let texture = upload_texture_slice_to_gpu(render_ctx, tensor, state.slice())?;
 
     let color_mapping = state.color_mapping();
 
     Ok(ColormappedTexture {
         texture,
-        decode_srgb: false,
         range,
+        decode_srgb: false,
+        multiply_rgb_with_alpha: false,
         gamma: color_mapping.gamma,
         color_mapper: Some(re_renderer::renderer::ColorMapper::Function(
             color_mapping.map,

crates/re_viewer_context/src/gpu_bridge/mod.rs

@@ -25,28 +25,59 @@ pub enum RangeError {
     /// This is weird. Should only happen with JPEGs, and those should have been decoded already
     #[error("Missing a range.")]
     MissingRange,
-
-    #[error("Non-finite range of values")]
-    NonfiniteRange,
 }
 
 /// Get a valid, finite range for the gpu to use.
-pub fn range(tensor_stats: &TensorStats) -> Result<[f32; 2], RangeError> {
-    let (min, max) = tensor_stats.range.ok_or(RangeError::MissingRange)?;
+pub fn tensor_data_range_heuristic(
+    tensor_stats: &TensorStats,
+    data_type: re_components::TensorDataType,
+) -> Result<[f32; 2], RangeError> {
+    let (min, max) = tensor_stats.finite_range.ok_or(RangeError::MissingRange)?;
 
     let min = min as f32;
     let max = max as f32;
 
-    if !min.is_finite() || !max.is_finite() {
-        Err(RangeError::NonfiniteRange)
+    // Apply heuristic for ranges that are typically expected depending on the data type and the finite (!) range.
+    // (we ignore NaN/Inf values heres, since they are usually there by accident!)
+    if data_type.is_float() && 0.0 <= min && max <= 1.0 {
+        // Float values that are all between 0 and 1, assume that this is the range.
+        Ok([0.0, 1.0])
+    } else if 0.0 <= min && max <= 255.0 {
+        // If all values are between 0 and 255, assume this is the range.
+        // (This is very common, independent of the data type)
+        Ok([0.0, 255.0])
     } else if min == max {
         // uniform range. This can explode the colormapping, so let's map all colors to the middle:
         Ok([min - 1.0, max + 1.0])
     } else {
+        // Use range as is if nothing matches.
         Ok([min, max])
     }
 }
 
+/// Return whether a tensor should be assumed to be encoded in sRGB color space ("gamma space", no EOTF applied).
+pub fn tensor_decode_srgb_gamma_heuristic(
+    tensor_stats: &TensorStats,
+    data_type: re_components::TensorDataType,
+    channels: u32,
+) -> Result<bool, RangeError> {
+    if matches!(channels, 1 | 3 | 4) {
+        let (min, max) = tensor_stats.finite_range.ok_or(RangeError::MissingRange)?;
+        #[allow(clippy::if_same_then_else)]
+        if 0.0 <= min && max <= 255.0 {
+            // If the range is suspiciously reminding us of a "regular image", assume sRGB.
+            Ok(true)
+        } else if data_type.is_float() && 0.0 <= min && max <= 1.0 {
+            // Floating point images between 0 and 1 are often sRGB as well.
+            Ok(true)
+        } else {
+            Ok(false)
+        }
+    } else {
+        Ok(false)
+    }
+}
+
 // ----------------------------------------------------------------------------
 
 pub fn viewport_resolution_in_pixels(clip_rect: egui::Rect, pixels_from_point: f32) -> [u32; 2] {