Vis Comput DOI 10.1007/s00371-017-1399-0 ORIGINAL ARTICLE High-dynamic-range image recovery from ﬂash and non-ﬂash image pairs Hristina Hristova 1 · Olivier Le Meur 1 · Remi Cozot 1 · Kadi Bouatouch 1 © Springer-Verlag Berlin Heidelberg 2017 Abstract In this paper, we propose a novel method for creat- ing HDR images from only two images—ﬂash and non-ﬂash images. Our method consists of two main steps, namely brightness gamma correction and bi-local chromatic adap- tation transform (CAT). The brightness gamma correction performs series of increases and decreases of the non-ﬂash brightness and yields multiple images with various exposure values. The bi-local CAT enhances the quality of each com- puted image by recovering missing details, using information from the ﬂash image. The ﬁnal multi-exposure images are then merged together to compute an HDR image. An evalua- tion shows that our HDR images, obtained by using only two LDR images, are close to HDR images, obtained by combin- ing ﬁve manually taken multi-exposure images. Our method does not require the usage of a tripod and it is suitable for images of non-still objects, such as people, candle ﬂames. Keywords HDR · Image enhancement · Flash/non-ﬂash photography 1 Introduction High-dynamic range (HDR) images capture the luminance of real-world scenes, which ranges from extreme dark to direct sunlight. Details of both shadow and highlight areas, present in a high-dynamic scene, can be recovered in a single HDR image. In contrast, standard digital imaging produces low-dynamic-range (LDR) images, in which the luminance dynamics is replaced by the discrete luma range. The latter B Hristina Hristova hristina.hristova@irisa.fr 1 University of Rennes 1, Rennes, France limits the capture of details in scene shadow and highlight regions, resulting in an under-/over-exposure. The camera response function (CRF) gives the relation- ship between the luminance and the luma up to a scale factor. To this end, to recover an HDR image using standard digi- tal imaging, an estimation of the CRF and a detail recovery for black/white image pixels are required. The most com- mon way of creating an HDR image by respecting these two requirements is to merge multiple LDR images, taken at various exposure times and referred to, in this paper, as multi-exposure images. Despite the efﬁciency of multi-exposure methods, the pro- cess of creating an HDR image is usually time-consuming. First, users are required to use a tripod and to adjust the cam- era exposure time each time they take an image (if the camera does not include exposure bracketing function). Moreover, during the shooting process, misalignment could become an issue, especially when there are moving objects in the scene. To this end, more time is likely to be spent aligning the images in the hope of correcting ghosting artifacts. To represent the atmosphere and the details of a real- world environment, users often need to take more than three exposure images [25]. However, this may increase the risk of misalignment and noise. In the particular case of dark environments with a high luminance range, decreasing the exposure time allows to capture ﬁne details in the highlights, but may signiﬁcantly increase the levels of noise in the com- puted HDR image. Instead of taking several multi-exposure images of the same scene, we propose a method, in which we use only two images to recover an HDR image—a non-ﬂash image, taken at a certain exposure value, and its corresponding ﬂash image. Our method can also be used for low-dynamic scenes to enhance the quality of a non-ﬂash image with the help of a ﬂash image. Non-ﬂash images represent the gen- 123