Function adam7_generate

_plotly_utils/png.py:212–227

Generate the coordinates for the reduced scanlines of an Adam7 interlaced image of size `width` by `height` pixels. Yields a generator for each pass, and each pass generator yields a series of (x, y, xstep) triples, each one identifying a reduced scanline consisting of

(width, height)

def adam7_generate(width, height):
    """
    Generate the coordinates for the reduced scanlines
    of an Adam7 interlaced image
    of size `width` by `height` pixels.

    Yields a generator for each pass,
    and each pass generator yields a series of (x, y, xstep) triples,
    each one identifying a reduced scanline consisting of
    pixels starting at (x, y) and taking every xstep pixel to the right.
    """

    for xstart, ystart, xstep, ystep in adam7:
        if xstart >= width:
            continue
        yield ((xstart, y, xstep) for y in range(ystart, height, ystep))


# Models the 'pHYs' chunk (used by the Reader)