Components

Provides memory pointer to have direct access to the png contents

property Scanline[const Index: Integer]: Pointer;

Description
Like delphi TBitmap, TPNGObject now also supports direct access to the image contents (include to alpha information using AlphaScanline). This property is intended to be used by experienced graphics programmers. Also the contents depends on the current color type and bit depth values (See header property) as the table shows bellow:

Image kind	Number of bits for each pixel	Recommended typecast to access the scanline data
COLOR_GRAYSCALE - Each pixel is intensity from 0 to 2^BitDepth - 1   COLOR_PALETTE     - Each pixel is a index to the palette table
Bitdepth = 1	1 bit	pByteArray (windows.pas) (Except for 8 and 16, bit manangement algorithms should be used since there's more than one pixel per byte)
Bitdepth = 2	4 bits (not 2)
Bitdepth = 4	4 bits
Bitdepth = 8	1 byte
Bitdepth = 16    (Grayscale)	1 byte
COLOR_RGB - Each pixel contains values for Red, Green, Blue intensities   COLOR_RGBALPHA - Same as RGB but followed by an Alpha Value   COLOR_GRAYSCALEALPHA - Same as GRAYSCALE but with alpha value
Bitdepth = 8	1 byte per sample	TRGBLine = array[word] of TRGBTriple; pRGBLine = ^TRGBLine;
Bitdepth = 16	1 byte per sample

Note: For BitDepth = 16 images, the extra information may be accessed with ExtraScanline property.