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use byteorder::{WriteBytesExt, LittleEndian};
use std::io::{self, Write};
use color::{ColorType, bits_per_pixel};
use png::PNGEncoder;
const ICO_IMAGE_TYPE: u16 = 1;
const ICO_ICONDIR_SIZE: u32 = 6;
const ICO_DIRENTRY_SIZE: u32 = 16;
pub struct ICOEncoder<W: Write> {
w: W
}
impl<W: Write> ICOEncoder<W> {
pub fn new(w: W) -> ICOEncoder<W> {
ICOEncoder {
w: w
}
}
pub fn encode(mut self, data: &[u8], width: u32, height: u32,
color: ColorType) -> io::Result<()> {
let mut image_data: Vec<u8> = Vec::new();
try!(PNGEncoder::new(&mut image_data).encode(
data, width, height, color));
try!(write_icondir(&mut self.w, 1));
try!(write_direntry(&mut self.w, width, height, color,
ICO_ICONDIR_SIZE + ICO_DIRENTRY_SIZE,
image_data.len() as u32));
try!(self.w.write_all(&image_data));
Ok(())
}
}
fn write_icondir<W: Write>(w: &mut W, num_images: u16) -> io::Result<()> {
try!(w.write_u16::<LittleEndian>(0));
try!(w.write_u16::<LittleEndian>(ICO_IMAGE_TYPE));
try!(w.write_u16::<LittleEndian>(num_images));
Ok(())
}
fn write_direntry<W: Write>(w: &mut W, width: u32, height: u32,
color: ColorType, data_start: u32,
data_size: u32) -> io::Result<()> {
try!(write_width_or_height(w, width));
try!(write_width_or_height(w, height));
try!(w.write_u8(0));
try!(w.write_u8(0));
try!(w.write_u16::<LittleEndian>(0));
try!(w.write_u16::<LittleEndian>(bits_per_pixel(color) as u16));
try!(w.write_u32::<LittleEndian>(data_size));
try!(w.write_u32::<LittleEndian>(data_start));
Ok(())
}
fn write_width_or_height<W: Write>(w: &mut W, value: u32) -> io::Result<()> {
if value < 1 || value > 256 {
return Err(io::Error::new(io::ErrorKind::InvalidData,
"Invalid ICO dimensions (width and \
height must be between 1 and 256)"));
}
w.write_u8(if value < 256 { value as u8 } else { 0 })
}