Mosaic images are captured by a single charge-coupled device/complementary metal-oxide-semiconductor (CCD/CMOS) sensor with the Bayer color filter array. We present a new quality-effective zooming algorithm for mosaic images. First, based on adaptive heterogeneity projection masks and Sobel- and luminance-estimation-based masks, more accurate gradient information is extracted from the mosaic image directly. According to the extracted gradient information, the mosaic green (G) channel is first zoomed. To reduce color artifacts, instead of directly moving the original red (R) value to its right position and the blue (B) value to its lower position, the color difference interpolation is utilized to expand the G-R and G-B color difference values. Finally, the zoomed mosaic R and B channels can be constructed using the zoomed G channel and the two expanded color difference values; afterward, the zoomed mosaic image is obtained. Based on 24 popular test mosaic images, experimental results demonstrate that the proposed zooming algorithm has more than 1.79 dB quality improvement when compared with two previous zooming algorithms, one by Battiato et al. (2002) and the other by Lukac et al. (2005).