Abstract: Examples of methods are described herein. In some examples, a method includes calculating a first cost function measure based on band defects in an image. In some examples, the method also includes calculating a second cost function measure based on the band defects and a synthetic band. In some examples, the method further includes detecting a missing band based on a comparison of the first cost function measure and the second cost function measure.

Abstract: Examples of methods are described herein. In some examples, a method includes calculating a first cost function measure based on band defects in an image. In some examples, the method also includes calculating a second cost function measure based on the band defects and a synthetic band. In some examples, the method further includes detecting a missing band based on a comparison of the first cost function measure and the second cost function measure.

Abstract: An example of an apparatus is provided. The apparatus includes a communication interface to receive an image of output from a printing device. The apparatus further includes a memory storage unit connected to the communication interface. The memory storage unit is to store the image of the output. The apparatus also includes a preprocessing engine to process the image. In addition, the apparatus includes a selective search engine to define a search area within the image. The selective search engine defines the search area of the image based on a local defect of unknown size. Furthermore, the apparatus includes a classification engine in communication with the selective search engine. The classification engine is to classify the search area for identification of the local defect.