/libjpeg/jcscale.c

https://code.google.com/p/xee/ · C · 62 lines · 38 code · 14 blank · 10 comment · 2 complexity · a774b925aa1c7d29f97d617615345f51 MD5 · raw file

  1. /*
  2. * jcscale.c
  3. *
  4. * Copyright (C) 1998, Thomas G. Lane.
  5. * This file is part of the Independent JPEG Group's software.
  6. * For conditions of distribution and use, see the accompanying README file.
  7. *
  8. * This file contains sample downscaling by 2^Pt for lossless JPEG.
  9. */
  10. #define JPEG_INTERNALS
  11. #include "jinclude.h"
  12. #include "jpeglib.h"
  13. #include "jlossls.h" /* Private declarations for lossless codec */
  14. #ifdef C_LOSSLESS_SUPPORTED
  15. METHODDEF(void)
  16. simple_downscale(j_compress_ptr cinfo,
  17. JSAMPROW input_buf, JSAMPROW output_buf, JDIMENSION width)
  18. {
  19. j_lossless_c_ptr losslsc = (j_lossless_c_ptr) cinfo->codec;
  20. int xindex;
  21. for (xindex = 0; xindex < width; xindex++)
  22. output_buf[xindex] = (JSAMPLE) RIGHT_SHIFT(GETJSAMPLE(input_buf[xindex]),
  23. cinfo->Al);
  24. }
  25. METHODDEF(void)
  26. noscale(j_compress_ptr cinfo,
  27. JSAMPROW input_buf, JSAMPROW output_buf, JDIMENSION width)
  28. {
  29. MEMCOPY(output_buf, input_buf, width * SIZEOF(JSAMPLE));
  30. return;
  31. }
  32. METHODDEF(void)
  33. scaler_start_pass (j_compress_ptr cinfo)
  34. {
  35. j_lossless_c_ptr losslsc = (j_lossless_c_ptr) cinfo->codec;
  36. /* Set scaler function based on Pt */
  37. if (cinfo->Al)
  38. losslsc->scaler_scale = simple_downscale;
  39. else
  40. losslsc->scaler_scale = noscale;
  41. }
  42. GLOBAL(void)
  43. jinit_c_scaler (j_compress_ptr cinfo)
  44. {
  45. j_lossless_c_ptr losslsc = (j_lossless_c_ptr) cinfo->codec;
  46. losslsc->scaler_start_pass = scaler_start_pass;
  47. }
  48. #endif /* C_LOSSLESS_SUPPORTED */