Adapting website images to Retina/HiDPI/high DPR devices
Most of Apple’s devices support this Device Pixel Ratio (DPR) of 2.0 (double physical resolution compared to logical resolution), including iPhone, iPad and Macbook Pro laptops. Android smartphones and tablets followed this trend, but there is a large variety of Android devices with different Device Pixel Ratios. For example, Samsung Galaxy S III has a DPR of 2.0, while the Samsung Galaxy S4 and LG G2 have a DPR of 3.0 (triple physical resolution). Some Android devices have non-round DPR values as well: 1.3, 1.5 and even 0.75.