Add jpeg_skip_scanlines() API to libjpeg-turbo

jdsample.c

 /*
  * jdsample.c
  *
  * This file was part of the Independent JPEG Group's software:
  * Copyright (C) 1991-1996, Thomas G. Lane.
  * libjpeg-turbo Modifications:
  * Copyright 2009 Pierre Ossman <ossman@cendio.se> for Cendio AB
  * Copyright (C) 2010, D. R. Commander.
  * For conditions of distribution and use, see the accompanying README file.
  *
  * This file contains upsampling routines.
  *
  * Upsampling input data is counted in "row groups".  A row group
  * is defined to be (v_samp_factor * DCT_scaled_size / min_DCT_scaled_size)
  * sample rows of each component.  Upsampling will normally produce
  * max_v_samp_factor pixel rows from each row group (but this could vary
  * if the upsampler is applying a scale factor of its own).
  *
  * An excellent reference for image resampling is
  *   Digital Image Warping, George Wolberg, 1990.
  *   Pub. by IEEE Computer Society Press, Los Alamitos, CA. ISBN 0-8186-8944-7.
  */
 
-#define JPEG_INTERNALS
-#include "jinclude.h"
-#include "jpeglib.h"
+#include "jdsample.h"
 #include "jsimd.h"
 #include "jpegcomp.h"
 
 
-/* Pointer to routine to upsample a single component */
-typedef JMETHOD(void, upsample1_ptr,
-                (j_decompress_ptr cinfo, jpeg_component_info * compptr,
-                 JSAMPARRAY input_data, JSAMPARRAY * output_data_ptr));
-
-/* Private subobject */
-
-typedef struct {
-  struct jpeg_upsampler pub;    /* public fields */
-
-  /* Color conversion buffer.  When using separate upsampling and color
-   * conversion steps, this buffer holds one upsampled row group until it
-   * has been color converted and output.
-   * Note: we do not allocate any storage for component(s) which are full-size,
-   * ie do not need rescaling.  The corresponding entry of color_buf[] is
-   * simply set to point to the input data array, thereby avoiding copying.
-   */
-  JSAMPARRAY color_buf[MAX_COMPONENTS];
-
-  /* Per-component upsampling method pointers */
-  upsample1_ptr methods[MAX_COMPONENTS];
-
-  int next_row_out;             /* counts rows emitted from color_buf */
-  JDIMENSION rows_to_go;        /* counts rows remaining in image */
-
-  /* Height of an input row group for each component. */
-  int rowgroup_height[MAX_COMPONENTS];
-
-  /* These arrays save pixel expansion factors so that int_expand need not
-   * recompute them each time.  They are unused for other upsampling methods.
-   */
-  UINT8 h_expand[MAX_COMPONENTS];
-  UINT8 v_expand[MAX_COMPONENTS];
-} my_upsampler;
-
-typedef my_upsampler * my_upsample_ptr;
-
 
 /*
  * Initialize for an upsampling pass.
  */
 
 METHODDEF(void)
 start_pass_upsample (j_decompress_ptr cinfo)
 {
   my_upsample_ptr upsample = (my_upsample_ptr) cinfo->upsample;
 
@@ skipping 410 matching lines @@
       ERREXIT(cinfo, JERR_FRACT_SAMPLE_NOTIMPL);
     if (need_buffer) {
       upsample->color_buf[ci] = (*cinfo->mem->alloc_sarray)
         ((j_common_ptr) cinfo, JPOOL_IMAGE,
          (JDIMENSION) jround_up((long) cinfo->output_width,
                                 (long) cinfo->max_h_samp_factor),
          (JDIMENSION) cinfo->max_v_samp_factor);
     }
   }
 }