Techniques are provided to generate high or wide dynamic range image from two or more input images of different exposure settings by directly merging coefficients derived from the input images in a transform domain. Energy values may be determined from coefficients blocks derived from the input images. The energy values may be compared with thresholds to determine weight factors for the coefficient blocks. An output coefficient block in the transform domain, used in or used to generate the output image, may be determined as a weighted combination of the coefficient blocks in the transform domain derived from the input images. If input images are compressed in transform domain, an output image can be generated without performing decompression in transform domain.