read-scanlines ( byte-reader loading-png width height -- array )

Vocabulary

images.png

Inputs

byte-reader	an object
loading-png	an object
width	an object
height	an object

Outputs

array

an object

Definition

USING: accessors bitstreams io kernel math sequences ;

IN: images.png

:: read-scanlines
    ( byte-reader loading-png width height -- array )
    loading-png png-components-per-pixel :> #components
    loading-png bit-depth>> :> bit-depth bit-depth :> depth!
    #components width * :> count! #components bit-depth *
    width * 8 align 8 /i :> stride height
    [ stride 1 + byte-reader stream-read ] replicate
    #components bit-depth 16 = [ 2 * ] when reverse-png-filter
    bit-depth 16 = [ 8 depth! count 2 * count! ] when
    <msb0-bit-reader> :> br height
    [ count [ depth br read ] B{ } replicate-as 8 br align ]
    replicate concat ;