1. An image output apparatus comprising: a determination unit configured to determine whether a density of a document image exceeds a threshold; and a control unit configured to inhibit an output of a composite image including a two-dimensional bar code and the document image if the determination unit determines that the density exceeds the threshold, and configured to output the composite image including the two-dimensional bar code and the document image if the determination unit determines that the density does not exceed the threshold, wherein the control unit is configured to calculate a density of the document image for each block including a dot constituting the two-dimensional bar code, and is configured to determine whether the two-dimensional bar code is detectable by checking whether the calculated density exceeds a predetermined threshold, wherein the control unit is configured to inhibit the output of the composite image including the two-dimensional bar code and the document image, if it is determined that the two-dimensional bar code is undetectable, even when the determination unit determines that the density does not exceed the threshold.