Vips – 8.0: Operator index > By section > Header
Description: Reference for Vips-8.0: Operator index > By section > Header

#### Operator index > By section > Header [src]

libvips supports getting and setting image header data (including metadata) in a uniform way.

Use `vips_image_get_typeof()` to test for the existence and `GType` of a header field.

You can attach arbitrary metadata to images. Metadata is copied as images are processed, so all images which used this image as input, directly or indirectly, will have this same bit of metadata attached to them. Copying is implemented with reference-counted pointers, so it is efficient, even for large items of data. This does however mean that metadata items need to be immutable. Metadata is handy for things like ICC profiles or EXIF data.

Various convenience functions (e.g. `vips_image_set_int()`) let you easily attach simple types like numbers, strings and memory blocks to images. Use `vips_image_map()` to loop over an image’s fields, including all metadata.

Items of metadata are identified by strings. Some strings are reserved, for example the ICC profile for an image is known by convention as “icc-profile-data” (i.e. the `VIPS_META_ICC_NAME` constant).

If you save an image in `.v` format, all metadata (with a restriction, see below) is automatically saved for you in a block of XML at the end of the file. When you load a `.v` image, the metadata is restored. You can use the `vipsedit` command-line tool to extract or replace this block of XML.

`.v` metadata is based on `GValue`. See the docs for that system if you want to do fancy stuff such as defining a new metadata type. libvips defines a new `GValue` called `VipsSaveString`, a variety of string, see `vips_value_set_save_string()`. If your `GValue` can be transformed to `VipsSaveString`, it will be saved and loaded to and from `.v` files for you.

libvips provides a couple of base classes which implement reference-counted areas of memory. If you base your metadata on one of these types, it can be copied between images efficiently.

## Callbacks

- `VipsImageMapFn`

## Functions

- `vips_format_sizeof()`
- `vips_format_sizeof_unsafe()`
- `vips_interpretation_max_alpha()`
- `vips_interpretation_bands()`
- `vips_image_get_width()`
- `vips_image_get_height()`
- `vips_image_get_bands()`
- `vips_image_get_format()`
- `vips_image_get_format_max()`
- `vips_image_guess_format()`
- `vips_image_get_coding()`
- `vips_image_get_interpretation()`
- `vips_image_guess_interpretation()`
- `vips_image_get_xres()`
- `vips_image_get_yres()`
- `vips_image_get_xoffset()`
- `vips_image_get_yoffset()`
- `vips_image_get_filename()`
- `vips_image_get_mode()`
- `vips_image_get_scale()`
- `vips_image_get_offset()`
- `vips_image_get_page_height()`
- `vips_image_get_n_pages()`
- `vips_image_get_n_subifds()`
- `vips_image_get_orientation()`
- `vips_image_get_orientation_swap()`
- `vips_image_get_tile_width()`
- `vips_image_get_tile_height()`
- `vips_image_get_gainmap()`
- `vips_image_get_concurrency()`
- `vips_image_get_data()`
- `vips_image_init_fields()`
- `vips_image_set()`
- `vips_image_get()`
- `vips_image_get_as_string()`
- `vips_image_get_typeof()`
- `vips_image_remove()`
- `vips_image_map()`
- `vips_image_get_fields()`
- `vips_image_set_area()`
- `vips_image_get_area()`
- `vips_image_set_blob()`
- `vips_image_set_blob_copy()`
- `vips_image_get_blob()`
- `vips_image_get_int()`
- `vips_image_set_int()`
- `vips_image_get_double()`
- `vips_image_set_double()`
- `vips_image_get_string()`
- `vips_image_set_string()`
- `vips_image_print_field()`
- `vips_image_get_image()`
- `vips_image_set_image()`
- `vips_image_set_array_int()`
- `vips_image_get_array_int()`
- `vips_image_get_array_double()`
- `vips_image_set_array_double()`
- `vips_image_history_printf()`
- `vips_image_history_args()`
- `vips_image_get_history()`

## Constants

- `VIPS_META_EXIF_NAME`
- `VIPS_META_XMP_NAME`
- `VIPS_META_IPTC_NAME`
- `VIPS_META_PHOTOSHOP_NAME`
- `VIPS_META_ICC_NAME`
- `VIPS_META_IMAGEDESCRIPTION`
- `VIPS_META_RESOLUTION_UNIT`
- `VIPS_META_BITS_PER_SAMPLE`
- `VIPS_META_PALETTE`
- `VIPS_META_LOADER`
- `VIPS_META_SEQUENTIAL`
- `VIPS_META_ORIENTATION`
- `VIPS_META_PAGE_HEIGHT`
- `VIPS_META_N_PAGES`
- `VIPS_META_N_SUBIFDS`
- `VIPS_META_TILE_WIDTH`
- `VIPS_META_TILE_HEIGHT`
- `VIPS_META_CONCURRENCY`