Constant opencv::imgcodecs::IMWRITE_PNG_COMPRESSION

pub const IMWRITE_PNG_COMPRESSION: i32 = 16;

For PNG, it can be the compression level from 0 to 9. A higher value means a smaller size and longer compression time. If specified, strategy is changed to IMWRITE_PNG_STRATEGY_DEFAULT (Z_DEFAULT_STRATEGY). Default value is 1 (best speed setting).