containsBlackPoint(a /*int*/, b /*int*/, fixed /*int*/, horizontal) {
			const image = this.image;
			if (horizontal) {
				for (let x = a; x <= b; x++) {
					if (image.get(x, fixed)) {
						return true;
					}
				}
			}
			else {
				for (let y = a; y <= b; y++) {
					if (image.get(fixed, y)) {
						return true;
					}
				}
			}
			return false;
		}
Determines whether a segment contains a black point

@param a          min value of the scanned coordinate
@param b          max value of the scanned coordinate
@param fixed      value of fixed coordinate
@param horizontal set to true if scan must be horizontal, false if vertical
@return true if a black point has been found, else false.