What does the phrase “sun through the trees printing her dress with soft luminous paws” (Lines 14-16) mean as used in the poem? Poem:

I was four in this photograph fishing
with my grandparents at a lake in Michigan.
My brother squats in poison ivy.
His Davy Crockett cap
sits squared on his head so the raccoon tail
flounces down the back of his sailor suit.

My grandfather sits to the far right
in a folding chair,
and I know his left hand is on
the tobacco in his pants pocket
because I used to wrap it for him
every Christmas. Grandmother’s hips
bulge from the brush, she’s leaning
into the ice chest, sun through the trees
printing her dress with soft
luminous paws.

I am staring jealously at my brother;
the day before he rode his first horse, alone.
I was strapped in a basket
behind my grandfather.
He smelled of lemons. He's died—
but I remember his hands.