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use byteorder::{LittleEndian, WriteBytesExt};
use std::io::{self, Write};
use crate::color::ColorType;
use crate::error::ImageResult;
use crate::image::ImageEncoder;
use crate::png::PNGEncoder;
// Enum value indicating an ICO image (as opposed to a CUR image):
const ICO_IMAGE_TYPE: u16 = 1;
// The length of an ICO file ICONDIR structure, in bytes:
const ICO_ICONDIR_SIZE: u32 = 6;
// The length of an ICO file DIRENTRY structure, in bytes:
const ICO_DIRENTRY_SIZE: u32 = 16;
/// ICO encoder
pub struct ICOEncoder<W: Write> {
w: W,
}
impl<W: Write> ICOEncoder<W> {
/// Create a new encoder that writes its output to ```w```.
pub fn new(w: W) -> ICOEncoder<W> {
ICOEncoder { w }
}
/// Encodes the image ```image``` that has dimensions ```width``` and
/// ```height``` and ```ColorType``` ```c```. The dimensions of the image
/// must be between 1 and 256 (inclusive) or an error will be returned.
pub fn encode(
mut self,
data: &[u8],
width: u32,
height: u32,
color: ColorType,
) -> ImageResult<()> {
let mut image_data: Vec<u8> = Vec::new();
PNGEncoder::new(&mut image_data).encode(data, width, height, color)?;
write_icondir(&mut self.w, 1)?;
write_direntry(
&mut self.w,
width,
height,
color,
ICO_ICONDIR_SIZE + ICO_DIRENTRY_SIZE,
image_data.len() as u32,
)?;
self.w.write_all(&image_data)?;
Ok(())
}
}
impl<W: Write> ImageEncoder for ICOEncoder<W> {
fn write_image(
self,
buf: &[u8],
width: u32,
height: u32,
color_type: ColorType,
) -> ImageResult<()> {
self.encode(buf, width, height, color_type)
}
}
fn write_icondir<W: Write>(w: &mut W, num_images: u16) -> io::Result<()> {
// Reserved field (must be zero):
w.write_u16::<LittleEndian>(0)?;
// Image type (ICO or CUR):
w.write_u16::<LittleEndian>(ICO_IMAGE_TYPE)?;
// Number of images in the file:
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<()> {
// Image dimensions:
write_width_or_height(w, width)?;
write_width_or_height(w, height)?;
// Number of colors in palette (or zero for no palette):
w.write_u8(0)?;
// Reserved field (must be zero):
w.write_u8(0)?;
// Color planes:
w.write_u16::<LittleEndian>(0)?;
// Bits per pixel:
w.write_u16::<LittleEndian>(color.bits_per_pixel())?;
// Image data size, in bytes:
w.write_u32::<LittleEndian>(data_size)?;
// Image data offset, in bytes:
w.write_u32::<LittleEndian>(data_start)?;
Ok(())
}
/// Encode a width/height value as a single byte, where 0 means 256.
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 })
}
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