The access to information displayed in public spaces is a challenge faced by visually impaired people for which image processing techniques have the potential to deliver satisfactory solutions. However, object recognition algorithms must initially locate possible candidates in the images, which is a hard task in complex scenes. In this article, we introduce an image processing technique that relies on the incorporation of markers to panels and boards with fixed layouts displaying dynamic content. The markers allow: A) locating the objects to be recognized; b) correcting perspective in the input images; c) limiting the training set size for supervised learning; and d) guiding the visually impaired by indicating how they should position their devices for adequate pictures. The proposed technique can be used for automatic recognition of texts and images and is suitable for deployment on mobile devices, providing more independence to the citizens. Results of preliminary tests on vending machines show that this method is robust enough to be used in practice. Copyright 2014 ACM.