Data sources

VIPS has data sources which can supply pixels for processing from a variety of sources. VIPS can stream images from files in VIPS native format, from tiled TIFF files, from binary PPM/PGM/PBM/PFM, from Radiance (HDR) files, from FITS images and from tiled OpenEXR images. VIPS will automatically unpack other formats to temporary disc files for you but this can obviously generate a lot of disc traffic. It also has a special sequential mode for streaming operations on non-random-access formats. Another section in these docs explains how libvips opens a file. One of the sources uses the ImageMagick (or optionally GraphicsMagick) library, so VIPS can read any image format that these libraries can read.

VIPS images are held on disc as a 64-byte header containing basic image information like width, height, bands and format, then the image data as a single large block of pixels, left-to-right and top-to-bottom, then an XML extension block holding all the image metadata, such as ICC profiles and EXIF blocks.

When reading from a large VIPS image (or any other format with the same structure on disc, such as binary PPM), VIPS keeps a set of small rolling windows into the file, some small number of scanlines in size. As pixels are demanded by different threads VIPS will move these windows up and down the file. As a result, VIPS can process images much larger than RAM, even on 32-bit machines.