Function png::expand_interlaced_row
source ยท pub fn expand_interlaced_row(
img: &mut [u8],
img_row_stride: usize,
interlaced_row: &[u8],
interlace_info: &Adam7Info,
bits_per_pixel: u8,
)
Expand description
Copies pixels from interlaced_row
into the right location in img
.
First bytes of img
should belong to the top-left corner of the currently decoded frame.
img_row_stride
specifies an offset in bytes between subsequent rows of img
.
This can be the width of the current frame being decoded, but this is not required - a bigger
stride may be useful if the frame being decoded is a sub-region of img
.
interlaced_row
and interlace_info
typically come from
crate::decoder::Reader::next_interlaced_row, but this is not required. In particular, before
calling expand_interlaced_row
one may need to expand the decoded row, so that its format and
bits_per_pixel
matches that of img
. Note that in initial Adam7 passes the interlaced_row
may contain less pixels that the width of the frame being decoded (e.g. it contains only 1/8th
of pixels in the initial pass).
Example:
use png::{expand_interlaced_row, Adam7Info};
let info = Adam7Info::new(5, 0, 4); // 1st line of 5th pass has 4 pixels.
let mut img = vec![0; 8 * 8];
let row = vec![1, 2, 3, 4];
expand_interlaced_row(&mut img, 8, &row, &info, 8);
assert_eq!(&img, &[
0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0,
1, 0, 2, 0, 3, 0, 4, 0, // <= this is where the 1st line of 5s appears
0, 0, 0, 0, 0, 0, 0, 0, // in the schematic drawing of the passes at
0, 0, 0, 0, 0, 0, 0, 0, // https://en.wikipedia.org/wiki/Adam7_algorithm
0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0,
]);