biYPelsPerMeter

biYPelsPerMeter is a metadata field in the Windows bitmap file formats, specifically within the BITMAPINFOHEADER. It records the vertical resolution of an image in units of pixels per meter. Its horizontal counterpart is biXPelsPerMeter. Together, these fields describe how large an image should appear when printed or displayed at a physical size.

The values are 32-bit signed integers. A value of 0 means the resolution is unspecified. Nonzero values indicate the intended pixel density in the vertical direction; the horizontal value conveys the same idea for the horizontal direction. To relate these values to the more familiar dots per inch (DPI), you can convert using the factor 39.3701 pixels per meter per inch. For example, a biYPelsPerMeter of about 11811 corresponds to 300 DPI.

Usage and implications: These fields serve as metadata that can help software estimate the physical size of an image, particularly for printing. They are not guaranteed to be respected by all programs, and some workflows rely on explicit DPI settings rather than biYPelsPerMeter. If width and height in pixels are known, you can compute the physical height by dividing the pixel height by biYPelsPerMeter (and similarly for width).

Notes: Since many image viewers and printers do not rely on these values, biYPelsPerMeter should not be used as the sole indicator of an image’s size. It is one of several related metadata fields, alongside biXPelsPerMeter, and is part of the BMP/DIB header used to convey resolution information for raster images.