Can it be filled with other colors, such as blue, red

[2424004764]

After deleting the background, the default color is white, can it be filled with other colors, such as red

[sunkangchina]

convert is good for add background image. its from ImageMagick. code like

$cmd = "convert $file_1 -background '".$color."'  -flatten $file_2";

if your are useing PHP or just command line

convert input_file  -background 'blue|red|..'  -flatten output_file