watermark static method
Implementation
static String watermark(String imageUrl, int x, int y, int transparency) {
if (imageUrl.isEmpty) {
throw ArgumentError('Image URL must not be blank.');
}
if (transparency < 0 || transparency > 100) {
throw ArgumentError('Transparency must be between 0 and 100, inclusive.');
}
return '$_filterWatermark($imageUrl,$x,$y,$transparency)';
}