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extern crate png;
#[derive(Debug)]
pub enum DecodeErrorPNG {
NotPNG,
BadNum,
GrayscaleNYI,
IndexedNYI,
AGrayscaleNYI,
BitsNYI,
}
impl ::std::fmt::Display for DecodeErrorPNG {
fn fmt(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
write!(f, "Couldn't parse PNG because: {}", match *self {
DecodeErrorPNG::NotPNG => "Not a PNG file (bad header)",
DecodeErrorPNG::BadNum => "Dimensions are not numbers",
DecodeErrorPNG::GrayscaleNYI => "NYI: Grayscale",
DecodeErrorPNG::IndexedNYI => "NYI: Indexed",
DecodeErrorPNG::AGrayscaleNYI => "NYI: AGrayscale",
DecodeErrorPNG::BitsNYI => "NYI: bad bits",
})
}
}
pub fn decode(png: &'static [u8]) -> Result<Vec<u32>, DecodeErrorPNG> {
use png::ColorType::*;
let decoder = png::Decoder::new(png);
let (info, mut reader) = decoder.read_info().unwrap();
let mut buf = vec![0; info.buffer_size()];
reader.next_frame(&mut buf).unwrap();
let size = (info.width * info.height) as usize;
let mut out = Vec::with_capacity(size + 2);
unsafe {
out.set_len(size + 2);
}
out[0] = info.width;
out[1] = info.height;
let (color, bit) = reader.output_color_type();
match color {
RGB => {
let mut pixel: [u8; 4] = unsafe {
::std::mem::uninitialized()
};
for i in 0..size {
pixel[0] = buf[i * 3 + 2];
pixel[1] = buf[i * 3 + 1];
pixel[2] = buf[i * 3 + 0];
pixel[3] = 0xFF;
out[2 + i] = unsafe {
::std::mem::transmute(pixel)
};
}
},
RGBA => {
let mut pixel: [u8; 4] = unsafe {
::std::mem::uninitialized()
};
for i in 0..size {
pixel[0] = buf[i * 4 + 2];
pixel[1] = buf[i * 4 + 1];
pixel[2] = buf[i * 4 + 0];
pixel[3] = buf[i * 4 + 3];
out[2 + i] = unsafe {
::std::mem::transmute(pixel)
};
}
},
Grayscale => return Err(DecodeErrorPNG::GrayscaleNYI),
Indexed => return Err(DecodeErrorPNG::IndexedNYI),
GrayscaleAlpha => return Err(DecodeErrorPNG::AGrayscaleNYI),
}
if bit != png::BitDepth::Eight {
return Err(DecodeErrorPNG::BitsNYI)
}
Ok(out)
}