Class: JPEG::Decoder

Inherits:
Object
  • Object
show all
Defined in:
ext/jpeg/jpeg.c

Instance Method Summary collapse

Constructor Details

#initialize(opts) ⇒ Object

initialize decoder object

Parameters:

  • opts (Hash) —

    options to initialize object

Options Hash (opts):

  • :pixel_format (Symbol) —

    specifies the format of the output image. possible values are: YUV422 YUYV RGB565 RGB RGB24 BGR BGR24 YUV444 YCbCr RGBX RGB32 BGRX BGR32 GRAYSCALE

  • :output_gamma (Float)
  • :fancy_upsampling (Boolean)
  • :do_smoothing (Boolean)
  • :dither (Array) —

    specifies dithering parameters. A 3-elements array. specify the dither type as a string for the 1st element, whether to use 2-pass quantize for the 2nd element as a boolean, and the number of colors used for the 3rd element as an integer from 16 to 256.

  • :without_meta (Boolean) —

    specifies whether or not to include meta information in the output data. If true, no meta-information is output.

  • :expand_colormap (Boolean) —

    specifies whether to expand the color map. If dither is specified, the output will be a color number of 1 byte per pixel, but if this option is set to true, the output will be expanded to color information.

  • :scale (Ratioanl)
  • :dct_method (Symbol) —

    specifies how decoding is handled. possible values are: FASTEST ISLOW IFAST FLOAT

  • :with_exif_tags (Boolean) —

    specifies whether to include Exif tag information in the output data. set this option to true to parse the Exif tag information and include it in the meta information output.

  • :with_exif (Boolean) —

    alias to :with_exif_tags option.



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# File 'ext/jpeg/jpeg.c', line 2001

static VALUE
rb_decoder_initialize( int argc, VALUE *argv, VALUE self)
{
  jpeg_decode_t* ptr;
  VALUE exc;
  VALUE opt;

  /*
   * initialize
   */
  TypedData_Get_Struct(self, jpeg_decode_t, &jpeg_decoder_data_type, ptr);

  /*
   * parse arguments
   */
  rb_scan_args( argc, argv, "0:", &opt);

  /*
   * set context
   */ 
  exc = set_decoder_context(ptr, opt);

  /*
   * post process
   */
  if (RTEST(exc)) rb_exc_raise(exc);

  return Qtrue;
}

Instance Method Details

#decode(jpeg) ⇒ String Also known as: decompress, <<

decode JPEG data

Returns decoded raw image data.

Parameters:

  • jpeg (String) —

    JPEG data to decode.

Returns:

  • (String) —

    decoded raw image data.



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# File 'ext/jpeg/jpeg.c', line 3669

static VALUE
rb_decoder_decode(VALUE self, VALUE data)
{
  VALUE ret;
  jpeg_decode_t* ptr;
  int state;

  /*
   * initialize
   */
  ret   = Qnil;
  state = 0;

  TypedData_Get_Struct(self, jpeg_decode_t, &jpeg_decoder_data_type, ptr);

  /*
   * argument check
   */
  Check_Type(data, T_STRING);

  /*
   * prepare
   */
  SET_DATA(ptr, data);

  /*
   * do decode
   */
  ret = rb_protect(do_decode, (VALUE)ptr, &state);

  /*
   * post process
   */
  CLR_DATA(ptr);

  if (state != 0) rb_jump_tag(state);

  return ret;
}

#read_header(jpeg) ⇒ JPEG::Meta

read meta data

Returns metadata.

Parameters:

  • jpeg (String) —

    input data.

Returns:



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# File 'ext/jpeg/jpeg.c', line 3020

static VALUE
rb_decoder_read_header(VALUE self, VALUE data)
{
  VALUE ret;
  jpeg_decode_t* ptr;
  int state;

  /*
   * initialize
   */
  ret   = Qnil;
  state = 0;

  TypedData_Get_Struct(self, jpeg_decode_t, &jpeg_decoder_data_type, ptr);

  /*
   * argument check
   */
  Check_Type(data, T_STRING);

  /*
   * prepare
   */
  SET_DATA(ptr, data);

  /*
   * do encode
   */
  ret = rb_protect(do_read_header, (VALUE)ptr, &state);

  /*
   * post process
   */
  CLR_DATA(ptr);

  if (state != 0) rb_jump_tag(state);

  return ret;
}

#set(opt) ⇒ Object 



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# File 'ext/jpeg/jpeg.c', line 2031

static VALUE
rb_decoder_set(VALUE self, VALUE opt)
{
  jpeg_decode_t* ptr;
  VALUE exc;

  /*
   * initialize
   */
  TypedData_Get_Struct(self, jpeg_decode_t, &jpeg_decoder_data_type, ptr);

  /*
   * check argument
   */
  Check_Type(opt, T_HASH);

  /*
   * set context
   */ 
  exc = set_decoder_context(ptr, opt);

  /*
   * post process
   */
  if (RTEST(exc)) rb_exc_raise(exc);

  return Qtrue;
}