Start fixes for the gasket example

The image is inverted for reasons I don't entirely understand yet

enkou-shaders/examples/gasket.rs

@@ -5,8 +5,8 @@ use enkou_shaders::camera::entry::main_image_render;
 use enkou_shaders::chaos_game::entry::main_chaos_game;
 use enkou_shaders::transform::Transform;
 use enkou_shaders::variation::Variation;
-use glam::{Affine2, UVec2, Vec2, Vec4, uvec2, vec2};
-use image::{Rgba, Rgba32FImage};
+use glam::{Affine2, UVec2, Vec2, Vec2Swizzles, Vec4, uvec2, vec2};
+use image::{Rgba, RgbaImage};
 use std::mem;
 use std::process::Command;
 use tempfile::NamedTempFile;
@@ -65,7 +65,7 @@ pub fn main() -> Result<()> {
     let palette = &[Vec4::ONE; 2];
 
     let mut output_points_pixel = Vec::new();
-    output_points_pixel.resize(ITERATIONS as usize, Vec4::ZERO);
+    output_points_pixel.resize(IMAGE_DIMENSION.xy().element_product() as usize, Vec4::ZERO);
 
     main_image_render(
         &camera,
@@ -74,11 +74,16 @@ pub fn main() -> Result<()> {
         &mut output_points_pixel,
     );
 
-    let mut image = Rgba32FImage::new(IMAGE_DIMENSION.x, IMAGE_DIMENSION.y);
-    for x in 0..image.dimensions().0 {
+    let mut image = RgbaImage::new(IMAGE_DIMENSION.x, IMAGE_DIMENSION.y);
     for y in 0..image.dimensions().1 {
+        for x in 0..image.dimensions().0 {
             let pixel_index = y * IMAGE_DIMENSION.x + x;
             let pixel = output_points_pixel[pixel_index as usize];
+            let pixel = pixel.to_array().map(|channel| {
+                let channel = if channel.is_nan() { 0.0 } else { channel };
+                let channel = channel * u8::MAX as f32;
+                channel as u8
+            });
             image.put_pixel(x, y, Rgba(pixel.into()));
         }
     }

enkou-shaders/src/camera.rs

@@ -3,7 +3,7 @@
 //! Map points from the IFS coordinate system to pixel coordinates. This is a lossy transformation.
 use bytemuck::{Pod, Zeroable};
 use glam::{Affine2, IVec2, UVec2, Vec2, Vec4, Vec4Swizzles, vec2};
-use libm::{floorf, powf};
+use libm::{floorf, log10f, powf};
 
 /// Blending modes for mapping IFS color values (which are on a scale `[0, 1]`)
 /// to RGBA colors.
@@ -102,7 +102,11 @@ impl Camera {
 
     /// Map a point from IFS coordinates to a pixel index and RGBA value; if the IFS coordinate
     /// is outside the viewable range, return [`None`].
-    pub fn transform_point_to_image(&self, point: Vec4, palette: &[Vec4]) -> Option<(usize, Vec4)> {
+    pub fn transform_point_to_image_hist(
+        &self,
+        point: Vec4,
+        palette: &[Vec4],
+    ) -> Option<(usize, Vec4)> {
         let pixel_coordinates = self.transform_point(point.xy());
         if pixel_coordinates.x < 0
             || pixel_coordinates.y < 0
@@ -112,20 +116,29 @@ impl Camera {
             return None;
         }
 
-        let to_pixel_index = self.dimensions.with_y(0);
+        let to_pixel_index = self.dimensions.with_y(1);
         let pixel_index = pixel_coordinates.as_uvec2().dot(to_pixel_index) as usize;
 
         let rgba = self.blend_mode.ifs_to_rgb(point.w, palette);
 
         Some((pixel_index, rgba))
     }
+
+    /// Map an accumulated RGBA value to the final pixel color value
+    pub fn transform_image_hist_to_rgba(&self, pixel: Vec4) -> Vec4 {
+        if pixel.w <= 0.0 {
+            Vec4::ZERO
+        } else {
+            // TODO: Fix the bootleg gamma adjustment
+            (pixel * log10f(pixel.w) / (pixel.w * self.image_gamma)).clamp(Vec4::ZERO, Vec4::ONE)
+        }
+    }
 }
 
 #[allow(missing_docs)]
 pub mod entry {
     use crate::camera::Camera;
     use glam::Vec4;
-    use libm::log10f;
     use spirv_std::spirv;
 
     /// Render an output image from a list of IFS coordinates.
@@ -144,17 +157,16 @@ pub mod entry {
         #[spirv(storage_buffer, descriptor_set = 1, binding = 0)] image: &mut [Vec4],
     ) {
         for coordinate_index in 0..coordinates_ifs.len() {
-            camera
-                .transform_point_to_image(coordinates_ifs[coordinate_index], palette)
-                .map(|(pixel_index, rgba)| image[pixel_index] += rgba);
+            if let Some((pixel_index, rgba)) =
+                camera.transform_point_to_image_hist(coordinates_ifs[coordinate_index], palette)
+            {
+                image[pixel_index] += rgba;
+            }
         }
 
         for pixel_index in 0..image.len() {
-            // TODO: Fix the bootleg gamma adjustment
-            let pixel_unscaled = image[pixel_index];
-            let pixel =
-                pixel_unscaled * log10f(pixel_unscaled.w) / (pixel_unscaled.w * camera.image_gamma);
-            image[pixel_index] = pixel;
+            let rgba = camera.transform_image_hist_to_rgba(image[pixel_index]);
+            image[pixel_index] = rgba;
         }
     }
 }