A method that integrates tone mapping for high dynamic range (HDR) gray-scale images with JPEG
compression is proposed. The tone mapping operator (TMO) is block-based, and structured so that
the same discrete cosine transform (DCT) that is used for the JPEG compression serves to complete
a major part of the tone-mapping operation. Simulations have been done on high dynamic range
images from the Debevec library. Experimental results show the technique successfully tone maps
and compresses simultaneously; the number of bits per pixel is reduced from 32 to an average of
0.67 by the compression, with an average PSNR of 56.3 dB for the compressed tone-mapped images
compared to images that have been only tone-mapped. The output of the proposed method is an
image that requires only limited storage space, and can be decompressed with a standard JPEG
This paper describes the design of analog circuitry to implement logarithmic number system (LNS) subtraction. Such
circuitry, if incorporated in the readout circuitry of a logarithmic CMOS image sensor, would allow for the on-chip
calculation of spatial derivatives, while operating directly on logarithmically-scaled pixels. The circuit was implemented
for a 1.2μm CMOS process. The maximum relative error at the output of the LNS subtractor for pixel currents that
correspond to an illumination range of more than four decades is 4.26%.
This paper introduces a novel algorithm for the enhancement of images of large dynamic range. In addition to dynamic range compression, the method provides control of brightness and contrast. The dynamic range compression is done in the spatial domain using the log transformation. Brightness and contrast control are done in the biorthogonal 9/7 wavelet transform domain. The algorithm can be easily added on to a JPEG2000 image compression system with only a
modest increase in the computational complexity. Experimental results have shown comparable visual quality with the previously published Retinex algorithm.