/// <summary>
/// Jpeg_set_defaultses this instance.
/// </summary>
/// <remarks>Uses only the input image's color space (property <see cref="jpeg_compress_struct.In_color_space"/>,
/// which must already be set in <see cref="jpeg_compress_struct"/>). Many applications will only need
/// to use this routine and perhaps <see cref="jpeg_compress_struct.jpeg_set_quality"/>.
/// </remarks>
/// <seealso href="ce3f6712-3633-4a58-af07-626a4fba9ae4.htm" target="_self">Compression parameter selection</seealso>
public void jpeg_set_defaults()
{
/* Safety check to ensure start_compress not called yet. */
if (m_global_state != JpegState.CSTATE_START)
ERREXIT(J_MESSAGE_CODE.JERR_BAD_STATE, (int)m_global_state);
/* Allocate comp_info array large enough for maximum component count.
* Array is made permanent in case application wants to compress
* multiple images at same param settings.
*/
if (m_comp_info == null)
{
m_comp_info = jpeg_component_info.createArrayOfComponents(JpegConstants.MAX_COMPONENTS);
}
/* Initialize everything not dependent on the color space */
m_data_precision = JpegConstants.BITS_IN_JSAMPLE;
/* Set up two quantization tables using default quality of 75 */
jpeg_set_quality(75, true);
/* Set up two Huffman tables */
std_huff_tables();
/* Default is no multiple-scan output */
m_scan_info = null;
m_num_scans = 0;
/* Expect normal source image, not raw downsampled data */
m_raw_data_in = false;
/* By default, don't do extra passes to optimize entropy coding */
m_optimize_coding = false;
/* The standard Huffman tables are only valid for 8-bit data precision.
* If the precision is higher, force optimization on so that usable
* tables will be computed. This test can be removed if default tables
* are supplied that are valid for the desired precision.
*/
if (m_data_precision > 8)
m_optimize_coding = true;
/* By default, use the simpler non-cosited sampling alignment */
m_CCIR601_sampling = false;
/* No input smoothing */
m_smoothing_factor = 0;
/* DCT algorithm preference */
m_dct_method = JpegConstants.JDCT_DEFAULT;
/* No restart markers */
m_restart_interval = 0;
m_restart_in_rows = 0;
/* Fill in default JFIF marker parameters. Note that whether the marker
* will actually be written is determined by jpeg_set_colorspace.
*
* By default, the library emits JFIF version code 1.01.
* An application that wants to emit JFIF 1.02 extension markers should set
* JFIF_minor_version to 2. We could probably get away with just defaulting
* to 1.02, but there may still be some decoders in use that will complain
* about that; saying 1.01 should minimize compatibility problems.
*/
m_JFIF_major_version = 1; /* Default JFIF version = 1.01 */
m_JFIF_minor_version = 1;
m_density_unit = DensityUnit.Unknown; /* Pixel size is unknown by default */
m_X_density = 1; /* Pixel aspect ratio is square by default */
m_Y_density = 1;
/* Choose JPEG colorspace based on input space, set defaults accordingly */
jpeg_default_colorspace();
}
/// <summary>
/// Set default decompression parameters.
/// </summary>
private void default_decompress_parms()
{
/* Guess the input colorspace, and set output colorspace accordingly. */
/* (Wish JPEG committee had provided a real way to specify this...) */
/* Note application may override our guesses. */
switch (m_num_components)
{
case 1:
m_jpeg_color_space = J_COLOR_SPACE.JCS_GRAYSCALE;
m_out_color_space = J_COLOR_SPACE.JCS_GRAYSCALE;
break;
case 3:
if (m_saw_JFIF_marker)
{
/* JFIF implies YCbCr */
m_jpeg_color_space = J_COLOR_SPACE.JCS_YCbCr;
}
else if (m_saw_Adobe_marker)
{
switch (m_Adobe_transform)
{
case 0:
m_jpeg_color_space = J_COLOR_SPACE.JCS_RGB;
break;
case 1:
m_jpeg_color_space = J_COLOR_SPACE.JCS_YCbCr;
break;
default:
WARNMS(J_MESSAGE_CODE.JWRN_ADOBE_XFORM, m_Adobe_transform);
m_jpeg_color_space = J_COLOR_SPACE.JCS_YCbCr; /* assume it's YCbCr */
break;
}
}
else
{
/* Saw no special markers, try to guess from the component IDs */
int cid0 = m_comp_info[0].Component_id;
int cid1 = m_comp_info[1].Component_id;
int cid2 = m_comp_info[2].Component_id;
if (cid0 == 1 && cid1 == 2 && cid2 == 3)
{
/* assume JFIF w/out marker */
m_jpeg_color_space = J_COLOR_SPACE.JCS_YCbCr;
}
else if (cid0 == 82 && cid1 == 71 && cid2 == 66)
{
/* ASCII 'R', 'G', 'B' */
m_jpeg_color_space = J_COLOR_SPACE.JCS_RGB;
}
else
{
TRACEMS(1, J_MESSAGE_CODE.JTRC_UNKNOWN_IDS, cid0, cid1, cid2);
/* assume it's YCbCr */
m_jpeg_color_space = J_COLOR_SPACE.JCS_YCbCr;
}
}
/* Always guess RGB is proper output colorspace. */
m_out_color_space = J_COLOR_SPACE.JCS_RGB;
break;
case 4:
if (m_saw_Adobe_marker)
{
switch (m_Adobe_transform)
{
case 0:
m_jpeg_color_space = J_COLOR_SPACE.JCS_CMYK;
break;
case 2:
m_jpeg_color_space = J_COLOR_SPACE.JCS_YCCK;
break;
default:
WARNMS(J_MESSAGE_CODE.JWRN_ADOBE_XFORM, m_Adobe_transform);
/* assume it's YCCK */
m_jpeg_color_space = J_COLOR_SPACE.JCS_YCCK;
break;
}
}
else
{
/* No special markers, assume straight CMYK. */
m_jpeg_color_space = J_COLOR_SPACE.JCS_CMYK;
}
m_out_color_space = J_COLOR_SPACE.JCS_CMYK;
break;
default:
m_jpeg_color_space = J_COLOR_SPACE.JCS_UNKNOWN;
m_out_color_space = J_COLOR_SPACE.JCS_UNKNOWN;
break;
}
/* Set defaults for other decompression parameters. */
m_scale_num = 1; /* 1:1 scaling */
m_scale_denom = 1;
m_buffered_image = false;
m_raw_data_out = false;
m_dct_method = JpegConstants.JDCT_DEFAULT;
m_do_fancy_upsampling = true;
m_do_block_smoothing = true;
m_quantize_colors = false;
/* We set these in case application only sets quantize_colors. */
m_dither_mode = J_DITHER_MODE.JDITHER_FS;
m_two_pass_quantize = true;
m_desired_number_of_colors = 256;
m_colormap = null;
/* Initialize for no mode change in buffered-image mode. */
m_enable_1pass_quant = false;
m_enable_external_quant = false;
m_enable_2pass_quant = false;
}