c# - Hidden pixels in PNG -

i'm designing c# console application converts bitmap vector art (svg) looping through pixels, pixel color in order draw , fill corresponding vector art component color .

the issue i'm facing , when loop through pixels colors using code

bitmap img = (bitmap)image.fromfile(imagepath); (int x = 0; x < img.width; x++) {    (int y = 0; y < img.height; y++)    {       currentfill = img.getpixel(x, y).name ;    }  } 

at x , y black color (#afafaf) not exist in image (or can't seen naked eye) ! issue did not happen jpg or tiff formats instance..any ideas ?

png files can have alpha channel. color type has a property represents alpha (transparency).