stocking

commit 3a2c64c30f0b2fc03b986a67a36d689ac3feb4d4
Author: Bradley Gannon <bradley@bradleygannon.com>
Date:   Thu, 11 Dec 2025 14:14:11 -0500

Add Pixel and Image structs, PPM output, and test image

Complete Chapters 1 and 2

Diffstat:
A
.gitignore
 | 
3
+++
A
Cargo.lock
 | 
7
+++++++
A
Cargo.toml
 | 
6
++++++
A
src/main.rs
 | 
56
++++++++++++++++++++++++++++++++++++++++++++++++++++++++

4 files changed, 72 insertions(+), 0 deletions(-)
diff --git a/.gitignore b/.gitignore
@@ -0,0 +1,2 @@
+*.ppm
+/target+
\ No newline at end of file
diff --git a/Cargo.lock b/Cargo.lock
@@ -0,0 +1,7 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 4
+
+[[package]]
+name = "stocking"
+version = "0.1.0"
diff --git a/Cargo.toml b/Cargo.toml
@@ -0,0 +1,6 @@
+[package]
+name = "stocking"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]
diff --git a/src/main.rs b/src/main.rs
@@ -0,0 +1,56 @@
+#[derive(Clone, Copy, Default)]
+struct Pixel {
+    red: f32,
+    green: f32,
+    blue: f32,
+}
+
+struct Image {
+    data: Vec<Vec<Pixel>>,
+}
+
+fn scale_f32_to_u8(value: f32) -> u8 {
+    (value * 255.) as u8
+}
+
+impl Image {
+    fn new(width: usize, height: usize) -> Self {
+        Image {
+            data: vec![vec![Pixel::default(); width]; height],
+        }
+    }
+    fn to_ppm_string(&self) -> String {
+        let mut output = "P3\n".to_string();
+        let height = self.data.len();
+        let width = if height > 0 { self.data[0].len() } else { 0 };
+        output += &format!("{width} {height}\n");
+        output += "255\n";
+        for (row_idx, row_data) in self.data.iter().enumerate() {
+            eprintln!("Scanlines remaining: {}", height - row_idx);
+            for Pixel { red, green, blue } in row_data.iter() {
+                output += &format!(
+                    "{} {} {}\n",
+                    scale_f32_to_u8(*red),
+                    scale_f32_to_u8(*green),
+                    scale_f32_to_u8(*blue)
+                );
+            }
+        }
+        eprintln!("Done");
+        output
+    }
+}
+
+fn main() {
+    let (width, height) = (256, 256);
+    let mut image = Image::new(width, height);
+    for i in 0..width {
+        for j in 0..height {
+            let red = i as f32 / (width - 1) as f32;
+            let green = j as f32 / (height - 1) as f32;
+            let blue = 0.;
+            image.data[j][i] = Pixel { red, green, blue };
+        }
+    }
+    println!("{}", image.to_ppm_string());
+}