blp 0.1.37

Blizzard BLP image format reader/writer (Warcraft/World of Warcraft textures)
Documentation 
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use crate::core::mipmap::Mipmap;
use crate::core::types::{SourceKind, TextureType, Version};
use crate::error::error::BlpError;

pub const MAX_MIPS: usize = 16;
pub const HEADER_SIZE: u64 = 156;

/// Checks if buffer is a BLP file by signature
fn is_blp_file(buf: &[u8]) -> bool {
    // BLP files start with "BLP1" or "BLP2" signature (or just "BLP" prefix)
    buf.len() >= 3 && &buf[..3] == b"BLP"
}

#[derive(Debug, Default)]
pub struct ImageBlp {
    #[allow(dead_code)]
    pub version: Version,
    pub texture_type: TextureType,
    pub compression: u8,
    pub alpha_bits: u32,
    pub alpha_type: u8,
    pub has_mips: u8,
    pub width: u32,
    pub height: u32,
    pub extra: u32,       // meaningful only if version <= BLP1
    pub has_mipmaps: u32, // meaningful only if version <= BLP1 or >= BLP2
    //
    pub mipmaps: Vec<Mipmap>,
    pub holes: usize,
    pub header_offset: usize,
    pub header_length: usize,
    //
    pub source: SourceKind,
}

impl ImageBlp {
    pub fn from_buf(buf: &[u8]) -> Result<Self, BlpError> {
        if is_blp_file(buf) {
            Self::from_buf_blp(buf)
        } else {
            Self::from_buf_image(buf)
        }
    }

    /// Create BLP from raw RGBA buffer.
    /// Buffer must be in RGBA format (4 bytes per pixel).
    /// Width and height must match the buffer size.
    pub fn from_rgba(rgba_buf: &[u8], width: u32, height: u32) -> Result<Self, BlpError> {
        Self::from_rgba_impl(rgba_buf, width, height)
    }

    /// Top-level decode entry.
    ///
    /// `mip_visible[i] == false` → skip decoding for mip `i`.
    /// Missing indices are treated as `true`.
    pub fn decode(&mut self, buf: &[u8], mip_visible: &[bool]) -> Result<(), BlpError> {
        match self.source {
            SourceKind::Blp => match self.texture_type {
                TextureType::DIRECT => self.decode_direct(buf, mip_visible),
                TextureType::JPEG => self.decode_jpeg(buf, mip_visible),
            },
            SourceKind::Image => self.decode_image(buf, mip_visible),
        }
    }
}