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//! Common common used both by decoder and encoder
extern crate color_quant;
use std::mem;
use std::borrow::Cow;
/// Disposal method
#[derive(Debug, Copy, Clone)]
#[repr(u8)]
pub enum DisposalMethod {
/// StreamingDecoder is not required to take any action.
Any = 0,
/// Do not dispose.
Keep = 1,
/// Restore to background color.
Background = 2,
/// Restore to previous.
Previous = 3,
}
impl DisposalMethod {
/// Converts `u8` to `Option<Self>`
pub fn from_u8(n: u8) -> Option<DisposalMethod> {
if n <= 3 {
Some(unsafe { mem::transmute(n) })
} else {
None
}
}
}
/// Known GIF block types
#[derive(Debug, Copy, Clone)]
#[repr(u8)]
pub enum Block {
/// Image block.
Image = 0x2C,
/// Extension block.
Extension = 0x21,
/// Image trailer.
Trailer = 0x3B
}
impl Block {
/// Converts `u8` to `Option<Self>`
pub fn from_u8(n: u8) -> Option<Block> {
match n {
0x2C | 0x21 | 0x3B => {
Some(unsafe { mem::transmute(n) })
}
_ => None
}
}
}
/// Known GIF extensions
#[derive(Debug, Copy, Clone)]
#[repr(u8)]
pub enum Extension {
/// Text extension.
Text = 0x01,
/// Control extension.
Control = 0xF9,
/// Comment extension.
Comment = 0xFE,
/// Application extension.
Application = 0xFF
}
impl Extension {
/// Converts `u8` to `Option<Self>`
pub fn from_u8(n: u8) -> Option<Extension> {
match n {
0x01 | 0xF9 | 0xFE | 0xFF => {
Some(unsafe { mem::transmute(n) })
}
_ => None
}
}
}
/// A GIF frame
#[derive(Debug, Clone)]
pub struct Frame<'a> {
/// Frame delay.
pub delay: u16,
/// Disposal method.
pub dispose: DisposalMethod,
/// Transparent index (if available).
pub transparent: Option<u8>,
/// True if the frame needs user input do be displayed.
pub needs_user_input: bool,
/// Offset from the top border of the canvas.
pub top: u16,
/// Offset from the left border of the canvas.
pub left: u16,
/// Width of the frame.
pub width: u16,
/// Height of the frame.
pub height: u16,
/// True if the image is interlaced.
pub interlaced: bool,
/// Frame local color palette if available.
pub palette: Option<Vec<u8>>,
/// Buffer containing the image data.
/// Only indices unless configured differently.
pub buffer: Cow<'a, [u8]>
}
impl<'a> Default for Frame<'a> {
fn default() -> Frame<'a> {
Frame {
delay: 0,
dispose: DisposalMethod::Keep,
transparent: None,
needs_user_input: false,
top: 0,
left: 0,
width: 0,
height: 0,
interlaced: false,
palette: None,
buffer: Cow::Borrowed(&[])
}
}
}
impl Frame<'static> {
/// Creates a frame from pixels in RGBA format.
///
/// *Note: This method is not optimized for speed.*
pub fn from_rgba(width: u16, height: u16, pixels: &mut [u8]) -> Frame<'static> {
assert_eq!(width as usize * height as usize * 4, pixels.len());
let mut frame = Frame::default();
let mut transparent = None;
for pix in pixels.chunks_mut(4) {
if pix[3] != 0 {
pix[3] = 0xFF;
} else {
transparent = Some([pix[0], pix[1], pix[2], pix[3]])
}
}
frame.width = width;
frame.height = height;
let nq = color_quant::NeuQuant::new(1, 256, pixels);
frame.buffer = Cow::Owned(pixels.chunks(4).map(|pix| nq.index_of(pix) as u8).collect());
frame.palette = Some(nq.color_map_rgb());
frame.transparent = if let Some(t) = transparent {
Some(nq.index_of(&t) as u8)
} else {
None
};
frame
}
/// Creates a frame from pixels in RGB format.
///
/// *Note: This method is not optimized for speed.*
pub fn from_rgb(width: u16, height: u16, pixels: &[u8]) -> Frame<'static> {
assert_eq!(width as usize * height as usize * 3, pixels.len());
let mut vec: Vec<u8> = Vec::with_capacity(pixels.len() + width as usize * height as usize);
for v in pixels.chunks(3) {
vec.extend([v[0], v[1], v[2], 0xFF].iter().cloned())
}
Frame::from_rgba(width, height, &mut vec)
}
}