[Feature] TextureBuilder Image Loading with Mipmap Generation

[vmarcella]

Overview

Add convenience methods to TextureBuilder for loading tsxtures directly from image files, with optional mipamp generation and sRGB format handling.

Current State

TextureBuilder requires manual pixel data:

// crates/lambda-rs/src/render/texture.rs
impl TextureBuilder {
  pub fn new_2d(format: TextureFormat) -> Self;
  pub fn with_size(mut self, width: u32, height: u32) -> Self;
  pub fn with_data(mut self, pixels: &[u8]) -> Self;
  // ...
}

Users must manually load images, decode them, and provide raw pixel bytes with the correct format.

Scope

• Add TextureBuilder::from_image(path) that loads and decodes common formats (PNG, JPEG, etc)
• Add TextureBuilder::from_image_bytes(bytes) for in-memory image data
• Automatically detect dimensions and select appropriate format (sRGB by default for color iamges)
• Add with_mipmaps(bool) to optionally generate mipmaps
• Add with_srgb(bool) override for explicit format control
• Investigate crates to use for loading images (Like image)

Proposed API

impl TextureBuilder {
  /// Load a texture from an image file path.
  /// Automatically determines dimensions and uses sRGB format for RGBA images.
  pub fn from_image(path: impl AsRef<Path>) -> Result<Self, ImageLoadError>;

  /// Load a texture from in-memory image bytes (PNG, JPEG, etc.).
  pub fn from_image_bytes(bytes: &[u8]) -> Result<Self, ImageLoadError>;

  /// Generate mipmaps for this texture (default: false).
  pub fn with_mipmaps(mut self, generate: bool) -> Self;

  /// Override the sRGB format selection (default: true for color images).
  pub fn with_srgb(mut self, srgb: bool) -> Self;
}

pub enum ImageLoadError {
  FileNotFound(PathBuf),
  DecodeError(String),
  UnsupportedFormat(String),
}

Example Usage

// Load texture from file with mipmaps
let texture = TextureBuilder::from_image("assets/diffuse.png")?
  .with_mipmaps(true)
  .with_label("diffuse-texture")
  .build(&mut render_context)?;

// Load from embedded bytes, override sRGB
let texture = TextureBuilder::from_image_bytes(include_bytes!("icon.png"))?
  .with_srgb(false)  // Linear color space
  .build(&mut render_context)?;

Acceptance criteria

• TextureBuilder::from_image(path) loads PNG, JPEG, and other common formats
• TextureBuilder::from_image_bytes(bytes) loads textures from in-memory data
• sRGB format selected by default for RGBA images
• with_srgb(bool) to override format
• with_mipmaps(bool) to generate mipmap levels
• ImageLoadError for making debugging issues with textures easier
• Investigate (and add) image to handle image loading data.
• Example demonstrating image loading
• Documentation for supported formats and mipmap behavior

Notes

• Mipmap generation may use box filtering or higher-quality downsampling
• Consider putting any newly added dependencies behind a feature
• Grayscale and other channel layouts should map to appropriate formats