YResolution

YResolution is a term used in digital imaging to describe the vertical sampling density of an image or the vertical resolution of a printing or scanning device. It is typically expressed in dots per inch (dpi) or pixels per inch (PPI) and is commonly stored as metadata alongside XResolution in various image formats and standards, including TIFF, JPEG EXIF, and PDF. The XResolution and YResolution values together indicate how many samples fit into each inch along the horizontal and vertical axes, respectively.

In practice, YResolution is used to relate pixel dimensions to physical size when printing or exporting to physical media. The printed height of an image is obtained by dividing the pixel height by the YResolution (assuming the units are inches), while the printed width is derived from the pixel width divided by the XResolution. The units are specified separately in the file, commonly as inches or centimeters; many formats default to inches.

Printers and scanners rely on YResolution to determine print quality and sampling density. Higher YResolution values yield finer vertical detail and smaller printed dimensions for a given pixel count, whereas lower values result in coarser vertical sampling or larger print sizes.

Common values vary by application: printers often use 300, 600, or 1200 dpi; screen-based workflows typically reference display PPI, though these are not always stored as YResolution. It is important to note that not all formats or software use YResolution, and changing it without resampling can alter the inferred print size without modifying pixel data.

In summary, YResolution is a key component in defining how a raster image corresponds to physical size in the vertical dimension, and it works in concert with XResolution to describe overall image density.