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3.3 Examples

As an example, figure 3.3 will print the width and height of an image stored on disc.

Figure 3.2: Print width and height of an image

To compile this example, use:

    cc `pkg-config vips-7.10 --cflags --libs` myfunc.c

As a slightly more complicated example, figure 3.3 will calculate the photographic negative of an image.

Figure 3.3: Find photographic negative

The call to `im_updatehist()` adds a line to the `Hist` field in `out`, noting the invocation of this program, its arguments, and the time and date at which it was run. It is the application's responsibility to keep `Hist` up-to-date -- the image processing functions do not use this field. You may also find `im_histlin()` helpful. It has type:

    void im_histlin( IMAGE *im,
      const char *fmt, ... )

It formats its arguments as `printf()` and appends the string formed to the `Hist` string.