Which format is commonly used for lossy compression of photographic images?

The JPEG format is commonly used for lossy compression of photographic images due to its ability to significantly reduce file size while maintaining an acceptable level of image quality. This is particularly important for photographs, which often contain a vast range of colors and gradients. JPEG compression works by analyzing the image and eliminating some of the data that the human eye is less likely to notice, such as subtle color changes.

By using techniques such as discrete cosine transform (DCT), JPEG can remove high-frequency information that is less perceptible to viewers, thus reducing the amount of data needed to store the image. This makes JPEG ideal for web use, where reduced loading times and bandwidth usage are critical. Additionally, JPEG supports a wide range of color depths, making it suitable for complex images like photographs.

In contrast, other formats like PNG and BMP are used for lossless compression, retaining all original image data. PNG is great for images that need transparency and relies on lossless compression, while BMP often results in much larger files since it typically does not compress image data at all. GIF is limited to a palette of 256 colors, making it unsuitable for high-quality photographs but useful for simple graphics and animations.