A new JPEG image enhancement method based on Retinex theory is proposed to improve the existing enhancement methods. The exiting methods cannot enhance images effectively because after JPEG compression images will lose some information. The proposed algorithm enhances images before quantization in the JPEG compression process to use full primal information of images. The discrete cosine transform (DCT) coefficients are divided into the incident component (DC coefficients) and the reflection component (AC coefficients) based on the Retinex theory; the DC coefficients are adjusted in the image dynamic range

and the AC coefficients are adjusted to enhance the details with the enhancement factors of the DC coefficients. The block artifacts will be suppressed by smoothing the DCT coefficients. Compared to other enhancement algorithms

results show the new approach’s efficiency in details enhancement and color preserving

while keeping the same compression ratio as the normal JPEG compression.