pub fn encode<I, W>(
    width: NonZeroUsize,
    height: NonZeroUsize,
    mut pixels: I,
    mut output: W,
) -> Result<usize, Error>
where
    I: Iterator<Item = Pixel>,
    W: Write,
{
    // Get our parameters into useful form
    let width = width.get();
    let height = height.get();

    let mut num_bytes = 0;
    let mut write = |buf: &[u8]| {
        num_bytes += buf.len();
        output.write_all(buf)
    };

    // Write the file header
    write(&MAGIC.to_be_bytes())?;
    write(&(width as u32).to_be_bytes())?;
    write(&(height as u32).to_be_bytes())?;
    write(&[4, 0])?;

    // A running lookup table of previously seen pixels
    let mut lookup = [Pixel::transparent(); 64];
    let mut prev = Pixel::rgba(0, 0, 0, 255);
    let mut run: u16 = 0;
    let num_pixels = width * height;
    let mut count = 0;

    while count < num_pixels {
        count += 1;

        // Get our next pixel, returning an error if the iterator runs dry
        let px = pixels.next().ok_or_else(|| Error::IteratorEmpty)?;

        // If multiple pixels are same in a row, increase the run-length
        if px == prev {
            run += 1;
        }

        // Check if we've got a run going, but we've hit the end of it
        if run > 0 && (run == 0x2020 || px != prev || count == num_pixels) {
            if run < 33 {
                // If it's a short run, encode it in 1 byte (RUN_8)
                run -= 1;
                write(&[RUN_8 | (run as u8)])?;
            } else {
                // If it's a long run, encode it in 2 bytes (RUN_16)
                run -= 33;
                write(&[RUN_16 | ((run >> 8) as u8), run as u8])?;
            }
            run = 0;
        }

        // If this pixel isn't a run
        if px != prev {
            let index_u8 = px.hash() % 64;
            let index = index_u8 as usize;
            if lookup[index] == px {
                // If our pixel is in the lookup table, we can just write an
                // index byte indicating which position in the table it's at
                write(&[INDEX | index_u8])?;
            } else {
                // If the pixel is different than the lookup value, overwrite it
                lookup[index] = px;

                // Get the difference between this and the previous pixel
                let vr = (px.r as i16) - (prev.r as i16);
                let vg = (px.g as i16) - (prev.g as i16);
                let vb = (px.b as i16) - (prev.b as i16);
                let va = (px.a as i16) - (prev.a as i16);

                // If the difference is small enough, we'll encode the pixel as a difference
                if vr > -17
                    && vr < 16
                    && vg > -17
                    && vg < 16
                    && vb > -17
                    && vb < 16
                    && va > -17
                    && va < 16
                {
                    if va == 0 && vr > -3 && vr < 2 && vg > -3 && vg < 2 && vb > -3 && vb < 2 {
                        // If the difference can be encoded in 2 bits for each channel,
                        // pack all 3 differences into one byte (DIFF_8)
                        write(&[DIFF_8 | ((((vr + 2) << 4) | (vg + 2) << 2 | (vb + 2)) as u8)])?;
                    } else if va == 0
                        && vr > -17
                        && vr < 16
                        && vg > -9
                        && vg < 8
                        && vb > -9
                        && vb < 8
                    {
                        // If the red difference fits in 5 bits and the green/blue fit in 4 bits,
                        // pack all the differences together into two bytes. (DIFF_16)
                        write(&[
                            DIFF_16 | ((vr + 16) as u8),
                            (((vg + 8) << 4) | (vb + 8)) as u8,
                        ])?;
                    } else {
                        // If each channel requires 5 bits to store its difference, then we pack
                        // them all into 3 bytes (DIFF_24)
                        write(&[
                            DIFF_24 | (((vr + 16) >> 1) as u8),
                            (((vr + 16) << 7) | ((vg + 16) << 2) | ((vb + 16) >> 3)) as u8,
                            (((vb + 16) << 5) | (va + 16)) as u8,
                        ])?;
                    }
                } else {
                    // This pixel is wholly unique, so we have to encode it. But instead of encoding
                    // the whole thing, we can check each of the RGBA channels and see if it is
                    // different than the previous pixel's. If it is, then we flag that channel's bit
                    // in the tag byte, and append the channel's color value.
                    let mut chunk = [COLOR, 0, 0, 0, 0];
                    let mut i = 1;
                    if px.r != prev.r {
                        chunk[0] |= 8;
                        chunk[i] = px.r;
                        i += 1;
                    }
                    if px.g != prev.g {
                        chunk[0] |= 4;
                        chunk[i] = px.g;
                        i += 1;
                    }
                    if px.b != prev.b {
                        chunk[0] |= 2;
                        chunk[i] = px.b;
                        i += 1;
                    }
                    if px.a != prev.a {
                        chunk[0] |= 1;
                        chunk[i] = px.a;
                        i += 1;
                    }
                    write(&chunk[..i])?;
                }
            }
        }

        // Store the pixel and move onto the next. We track the current pixel's index
        // as well so that if the last pixel is part of a run, we can finish the run
        prev = px;
    }

    // Mark the end of the data block with 4 empty bytes
    write(&[0, 0, 0, 0])?;

    // Return the total amount of bytes that were encoded
    Ok(num_bytes)
}
/// Encodes the pixels supplied by the `pixels` iterator into the `output` stream. The iterator is
/// expected to have `width * height` pixels in it. Returns the size of the encoded data.
Encodes the pixels supplied by the `pixels` iterator into the `output` stream. The iterator is
expected to have `width * height` pixels in it. Returns the size of the encoded data.
Encodes the pixels supplied by the ` pixels ` iterator into the ` output ` stream . The iterator is expected to have ` width * height ` pixels in it . Returns the size of the encoded data .
pub fn encode<I, W>(
    width: NonZeroUsize,
    height: NonZeroUsize,
    mut pixels: I,
    mut output: W,
) -> Result<usize, Error>
where
    I: Iterator<Item = Pixel>,
    W: Write,
{
    // Get our parameters into useful form
    let width = width.get();
    let height = height.get();
    let mut num_bytes = 0;
    let mut write = |buf: &[u8]| {
        num_bytes += buf.len();
        output.write_all(buf)
    };
    // Write the file header
    write(&MAGIC.to_be_bytes())?;
    write(&(width as u32).to_be_bytes())?;
    write(&(height as u32).to_be_bytes())?;
    write(&[4, 0])?;
    // A running lookup table of previously seen pixels
    let mut lookup = [Pixel::transparent(); 64];
    let mut prev = Pixel::rgba(0, 0, 0, 255);
    let mut run: u16 = 0;
    let num_pixels = width * height;
    let mut count = 0;
    while count < num_pixels {
        count += 1;
        // Get our next pixel, returning an error if the iterator runs dry
        let px = pixels.next().ok_or_else(|| Error::IteratorEmpty)?;
        // If multiple pixels are same in a row, increase the run-length
        if px == prev {
            run += 1;
        }
        // Check if we've got a run going, but we've hit the end of it
        if run > 0 && (run == 0x2020 || px != prev || count == num_pixels) {
            if run < 33 {
                // If it's a short run, encode it in 1 byte (RUN_8)
                run -= 1;
                write(&[RUN_8 | (run as u8)])?;
            } else {
                // If it's a long run, encode it in 2 bytes (RUN_16)
                run -= 33;
                write(&[RUN_16 | ((run >> 8) as u8), run as u8])?;
            }
            run = 0;
        }
        // If this pixel isn't a run
        if px != prev {
            let index_u8 = px.hash() % 64;
            let index = index_u8 as usize;
            if lookup[index] == px {
                // If our pixel is in the lookup table, we can just write an
                // index byte indicating which position in the table it's at
                write(&[INDEX | index_u8])?;
            } else {
                // If the pixel is different than the lookup value, overwrite it
                lookup[index] = px;
                // Get the difference between this and the previous pixel
                let vr = (px.r as i16) - (prev.r as i16);
                let vg = (px.g as i16) - (prev.g as i16);
                let vb = (px.b as i16) - (prev.b as i16);
                let va = (px.a as i16) - (prev.a as i16);
                // If the difference is small enough, we'll encode the pixel as a difference
                if vr > -17
                    && vr < 16
                    && vg > -17
                    && vg < 16
                    && vb > -17
                    && vb < 16
                    && va > -17
                    && va < 16
                {
                    if va == 0 && vr > -3 && vr < 2 && vg > -3 && vg < 2 && vb > -3 && vb < 2 {
                        // If the difference can be encoded in 2 bits for each channel,
                        // pack all 3 differences into one byte (DIFF_8)
                        write(&[DIFF_8 | ((((vr + 2) << 4) | (vg + 2) << 2 | (vb + 2)) as u8)])?;
                    } else if va == 0
                        && vr > -17
                        && vr < 16
                        && vg > -9
                        && vg < 8
                        && vb > -9
                        && vb < 8
                    {
                        // If the red difference fits in 5 bits and the green/blue fit in 4 bits,
                        // pack all the differences together into two bytes. (DIFF_16)
                        write(&[
                            DIFF_16 | ((vr + 16) as u8),
                            (((vg + 8) << 4) | (vb + 8)) as u8,
                        ])?;
                    } else {
                        // If each channel requires 5 bits to store its difference, then we pack
                        // them all into 3 bytes (DIFF_24)
                        write(&[
                            DIFF_24 | (((vr + 16) >> 1) as u8),
                            (((vr + 16) << 7) | ((vg + 16) << 2) | ((vb + 16) >> 3)) as u8,
                            (((vb + 16) << 5) | (va + 16)) as u8,
                        ])?;
                    }
                } else {
                    // This pixel is wholly unique, so we have to encode it. But instead of encoding
                    // the whole thing, we can check each of the RGBA channels and see if it is
                    // different than the previous pixel's. If it is, then we flag that channel's bit
                    // in the tag byte, and append the channel's color value.
                    let mut chunk = [COLOR, 0, 0, 0, 0];
                    let mut i = 1;
                    if px.r != prev.r {
                        chunk[0] |= 8;
                        chunk[i] = px.r;
                        i += 1;
                    }
                    if px.g != prev.g {
                        chunk[0] |= 4;
                        chunk[i] = px.g;
                        i += 1;
                    }
                    if px.b != prev.b {
                        chunk[0] |= 2;
                        chunk[i] = px.b;
                        i += 1;
                    }
                    if px.a != prev.a {
                        chunk[0] |= 1;
                        chunk[i] = px.a;
                        i += 1;
                    }
                    write(&chunk[..i])?;
                }
            }
        }
        // Store the pixel and move onto the next. We track the current pixel's index
        // as well so that if the last pixel is part of a run, we can finish the run
        prev = px;
    }
    // Mark the end of the data block with 4 empty bytes
    write(&[0, 0, 0, 0])?;
    // Return the total amount of bytes that were encoded
    Ok(num_bytes)
}
pub fn encode < I , W > ( width : NonZeroUsize , height : NonZeroUsize , mut pixels : I , mut output : W , ) -> Result < usize , Error > where I : Iterator < Item = Pixel > , W : Write , { // Get our parameters into useful form let width = width . get ( ) ; let height = height . get ( ) ; let mut num_bytes = 0 ; let mut write = | buf : & [ u8 ] | { num_bytes += buf . len ( ) ; output . write_all ( buf ) } ; // Write the file header write ( & MAGIC . to_be_bytes ( ) ) ? ; write ( & ( width as u32 ) . to_be_bytes ( ) ) ? ; write ( & ( height as u32 ) . to_be_bytes ( ) ) ? ; write ( & [ 4 , 0 ] ) ? ; // A running lookup table of previously seen pixels let mut lookup = [ Pixel :: transparent ( ) ; 64 ] ; let mut prev = Pixel :: rgba ( 0 , 0 , 0 , 255 ) ; let mut run : u16 = 0 ; let num_pixels = width * height ; let mut count = 0 ; while count < num_pixels { count += 1 ; // Get our next pixel, returning an error if the iterator runs dry let px = pixels . next ( ) . ok_or_else ( | | Error :: IteratorEmpty ) ? ; // If multiple pixels are same in a row, increase the run-length if px == prev { run += 1 ; } // Check if we've got a run going, but we've hit the end of it if run > 0 && ( run == 0x2020 || px != prev || count == num_pixels ) { if run < 33 { // If it's a short run, encode it in 1 byte (RUN_8) run -= 1 ; write ( & [ RUN_8 | ( run as u8 ) ] ) ? ; } else { // If it's a long run, encode it in 2 bytes (RUN_16) run -= 33 ; write ( & [ RUN_16 | ( ( run >> 8 ) as u8 ) , run as u8 ] ) ? ; } run = 0 ; } // If this pixel isn't a run if px != prev { let index_u8 = px . hash ( ) % 64 ; let index = index_u8 as usize ; if lookup [ index ] == px { // If our pixel is in the lookup table, we can just write an // index byte indicating which position in the table it's at write ( & [ INDEX | index_u8 ] ) ? ; } else { // If the pixel is different than the lookup value, overwrite it lookup [ index ] = px ; // Get the difference between this and the previous pixel let vr = ( px . r as i16 ) - ( prev . r as i16 ) ; let vg = ( px . g as i16 ) - ( prev . g as i16 ) ; let vb = ( px . b as i16 ) - ( prev . b as i16 ) ; let va = ( px . a as i16 ) - ( prev . a as i16 ) ; // If the difference is small enough, we'll encode the pixel as a difference if vr > - 17 && vr < 16 && vg > - 17 && vg < 16 && vb > - 17 && vb < 16 && va > - 17 && va < 16 { if va == 0 && vr > - 3 && vr < 2 && vg > - 3 && vg < 2 && vb > - 3 && vb < 2 { // If the difference can be encoded in 2 bits for each channel, // pack all 3 differences into one byte (DIFF_8) write ( & [ DIFF_8 | ( ( ( ( vr + 2 ) << 4 ) | ( vg + 2 ) << 2 | ( vb + 2 ) ) as u8 ) ] ) ? ; } else if va == 0 && vr > - 17 && vr < 16 && vg > - 9 && vg < 8 && vb > - 9 && vb < 8 { // If the red difference fits in 5 bits and the green/blue fit in 4 bits, // pack all the differences together into two bytes. (DIFF_16) write ( & [ DIFF_16 | ( ( vr + 16 ) as u8 ) , ( ( ( vg + 8 ) << 4 ) | ( vb + 8 ) ) as u8 , ] ) ? ; } else { // If each channel requires 5 bits to store its difference, then we pack // them all into 3 bytes (DIFF_24) write ( & [ DIFF_24 | ( ( ( vr + 16 ) >> 1 ) as u8 ) , ( ( ( vr + 16 ) << 7 ) | ( ( vg + 16 ) << 2 ) | ( ( vb + 16 ) >> 3 ) ) as u8 , ( ( ( vb + 16 ) << 5 ) | ( va + 16 ) ) as u8 , ] ) ? ; } } else { // This pixel is wholly unique, so we have to encode it. But instead of encoding // the whole thing, we can check each of the RGBA channels and see if it is // different than the previous pixel's. If it is, then we flag that channel's bit // in the tag byte, and append the channel's color value. let mut chunk = [ COLOR , 0 , 0 , 0 , 0 ] ; let mut i = 1 ; if px . r != prev . r { chunk [ 0 ] |= 8 ; chunk [ i ] = px . r ; i += 1 ; } if px . g != prev . g { chunk [ 0 ] |= 4 ; chunk [ i ] = px . g ; i += 1 ; } if px . b != prev . b { chunk [ 0 ] |= 2 ; chunk [ i ] = px . b ; i += 1 ; } if px . a != prev . a { chunk [ 0 ] |= 1 ; chunk [ i ] = px . a ; i += 1 ; } write ( & chunk [ .. i ] ) ? ; } } } // Store the pixel and move onto the next. We track the current pixel's index // as well so that if the last pixel is part of a run, we can finish the run prev = px ; } // Mark the end of the data block with 4 empty bytes write ( & [ 0 , 0 , 0 , 0 ] ) ? ; // Return the total amount of bytes that were encoded Ok ( num_bytes ) }
Encodes the pixels supplied by the `pixels` iterator into the `output` stream.
Encodes the pixels supplied by the ` pixels ` iterator into the ` output ` stream .
width
NonZeroUsize
height
NonZeroUsize
pixels
I
output
W
width
NonZeroUsize
height
NonZeroUsize
pixels
I
output
W