gp_resize.h

// SPDX-License-Identifier: LGPL-2.1-or-later
/*
 * Copyright (C) 2009-2013 Cyril Hrubis <metan@ucw.cz>
 */
 
/*
 
  gp_pixmap interpolations.
 
  Nearest Neighbour
  ~~~~~~~~~~~~~~~~~
 
  Fast, but produces pixelated images. Works however well for images with sharp
  edges mostly consisting of big one color regions (eg doesn't blur the
  result on upscaling).
 
  Bilinear
  ~~~~~~~~
 
  Faster than Bicubic, but less precise.
 
  Bilinear LF
  ~~~~~~~~~~~
 
  Bilinear with low-pass filter on downscaling, this is the best choice for
  fast up and downscaling.
 
  Bicubic
  ~~~~~~~
 
  Works well for upscaling as is. To get decent result on downscaling,
  low-pass filter (for example gaussian blur) must be used on original image
  before scaling is done.
 
 */
 
#ifndef FILTERS_GP_RESIZE_H
#define FILTERS_GP_RESIZE_H
 
#include <filters/gp_filter.h>
 
typedef enum gp_interpolation_type {
        GP_INTERP_NN,            /* Nearest Neighbour                         */
        GP_INTERP_LINEAR_INT,    /* Bilinear - fixed point arithmetics        */
        GP_INTERP_LINEAR_LF_INT, /* Bilinear + low pass filter on downscaling */
        GP_INTERP_CUBIC,         /* Bicubic                                   */
        GP_INTERP_CUBIC_INT,     /* Bicubic - fixed point arithmetics         */
        GP_INTERP_MAX = GP_INTERP_CUBIC_INT,
} gp_interpolation_type;
 
const char *gp_interpolation_type_name(enum gp_interpolation_type interp_type);
 
/*
 * Resize src to fit the dst, both src and dst must have the same pixel_type.
 *
 * Returns non-zero on error (interrupted from callback), zero on success.
 */
int gp_filter_resize(const gp_pixmap *src, gp_pixmap *dst,
                     gp_interpolation_type type,
                     gp_progress_cb *callback);
 
/*
 * Resize src to wxh, the result is allocated.
 *
 * Returns pointer to newly created pixmap.
 *
 * Returns NULL in case of failure and errno is set correspondinlgy.
 */
gp_pixmap *gp_filter_resize_alloc(const gp_pixmap *src,
                                  gp_size w, gp_size h,
                                  gp_interpolation_type type,
                                  gp_progress_cb *callback);
 
#endif /* FILTERS_GP_RESIZE_H */