APNG Encode

src/chunk.rs

@@ -1,6 +1,7 @@
 //! Chunk types and functions
 #![allow(dead_code)]
 #![allow(non_upper_case_globals)]
+#![allow(non_snake_case)]
 use core::fmt;
 
 #[derive(Clone, Copy, PartialEq, Eq, Hash)]
@@ -88,3 +89,42 @@ impl fmt::Debug for ChunkType {
             .finish()
     }
 }
+
+use crate::{BitDepth, ColorType};
+use io::Write;
+use std::io;
+
+pub fn encode_chunk<W: Write>(w: &mut W, chunk: ChunkType, data: &[u8]) -> io::Result<()> {
+    w.write_all(&(data.len() as u32).to_be_bytes())?;
+    w.write_all(&chunk.0)?;
+    w.write_all(data)?;
+
+    let mut crc = crc32fast::Hasher::new();
+    crc.update(&chunk.0);
+    crc.update(data);
+    w.write_all(&crc.finalize().to_be_bytes())
+}
+
+pub fn IHDR_encode<W: Write>(
+    w: &mut W,
+    width: u32,
+    height: u32,
+    bit_depth: BitDepth,
+    color_type: ColorType,
+    interlaced: bool,
+) -> io::Result<()> {
+    let mut data = [0; 13];
+    data[..4].copy_from_slice(&width.to_be_bytes());
+    data[4..8].copy_from_slice(&height.to_be_bytes());
+    data[8] = bit_depth as u8;
+    data[9] = color_type as u8;
+    data[12] = interlaced as u8;
+    encode_chunk(w, IHDR, &data)
+}
+
+pub fn fdAT_encode<W: Write>(w: &mut W, seq_num: u32, data: &[u8]) -> io::Result<()> {
+    let mut all_data = vec![0u8; 4 + data.len()];
+    all_data[..4].copy_from_slice(&seq_num.to_be_bytes());
+    all_data[4..].copy_from_slice(&data);
+    encode_chunk(w, fdAT, &all_data)
+}

src/common.rs

@@ -270,7 +270,7 @@ pub struct AnimationControl {
 }
 
 /// The type and strength of applied compression.
-#[derive(Debug, Clone)]
+#[derive(Debug, Clone, Copy)]
 pub enum Compression {
     /// Default level
     Default,