C# 클래스 BitMiracle.LibJpeg.Classic.jpeg_compress_struct

Abort processing of a JPEG compression operation.

Allows an arbitrary quantization table to be created.

Initializes a new instance of the jpeg_compress_struct class.

Initializes a new instance of the jpeg_compress_struct class.

Select an appropriate JPEG colorspace based on jpeg_compress_struct.In_color_space, and calls jpeg_compress_struct.jpeg_set_colorspace

This is actually a subroutine of jpeg_set_defaults. It's broken out in case you want to change just the colorspace-dependent JPEG parameters.

Set or change the 'quality' (quantization) setting, using default tables and straight percentage-scaling quality scales. This entry point allows different scalings for luminance and chrominance.

Finishes JPEG compression.

If a multipass operating mode was selected, this may do a great deal of work including most of the actual output.

Converts a value on the IJG-recommended quality scale to a linear scaling percentage.

Set the JPEG colorspace (property jpeg_compress_struct.Jpeg_color_space, and choose colorspace-dependent parameters appropriately.

See Special color spaces, below, before using this. A large number of parameters, including all per-component parameters, are set by this routine; if you want to twiddle individual parameters you should call jpeg_set_colorspace before rather than after.

Jpeg_set_defaultses this instance.

Uses only the input image's color space (property jpeg_compress_struct.In_color_space, which must already be set in jpeg_compress_struct). Many applications will only need to use this routine and perhaps jpeg_compress_struct.jpeg_set_quality.

Same as jpeg_set_quality except that the generated tables are the sample tables given in the JPEG specification section K.1, multiplied by the specified scale factor.

Note that larger scale factors give lower quality. This entry point is useful for conforming to the Adobe PostScript DCT conventions, but we do not recommend linear scaling as a user-visible quality scale otherwise.

Constructs JPEG quantization tables appropriate for the indicated quality setting.

Note that the exact mapping from quality values to tables may change in future IJG releases as more is learned about DCT quantization.

Generates a default scan script for writing a progressive-JPEG file.

This is the recommended method of creating a progressive file, unless you want to make a custom scan sequence. You must ensure that the JPEG color space is set correctly before calling this routine.

Starts JPEG compression.

Before calling this, all parameters and a data destination must be set up.

Sets output stream.

The caller must have already opened the stream, and is responsible for closing it after finishing compression.

Forcibly suppress or un-suppress all quantization and Huffman tables.

Marks all currently defined tables as already written (if suppress) or not written (if !suppress). This will control whether they get emitted by a subsequent jpeg_compress_struct.jpeg_start_compress call.
This routine is exported for use by applications that want to produce abbreviated JPEG datastreams.

Compression initialization for writing raw-coefficient data. Useful for lossless transcoding.

Before calling this, all parameters and a data destination must be set up. Call jpeg_finish_compress to actually write the data.

Writes a byte of special marker's data.

Writes special marker's header.

After calling this method you need to call jpeg_compress_struct.jpeg_write_m_byte exactly the number of times given in the length parameter.
This method lets you empty the output buffer partway through a marker, which might be important when using a suspending data destination module. In any case, if you are using a suspending destination, you should flush its buffer after inserting any special markers.

Write a special marker.

This is only recommended for writing COM or APPn markers. Must be called after jpeg_compress_struct.jpeg_start_compress and before first call to jpeg_compress_struct.jpeg_write_scanlines or jpeg_compress_struct.jpeg_write_raw_data.

Alternate entry point to write raw data.

Processes exactly one iMCU row per call, unless suspended. Replaces jpeg_write_scanlines when writing raw downsampled data.

Write some scanlines of data to the JPEG compressor.

We warn about excess calls to jpeg_write_scanlines() since this likely signals an application programmer error. However, excess scanlines passed in the last valid call are "silently" ignored, so that the application need not adjust num_lines for end-of-image when using a multiple-scanline buffer.

Alternate compression function: just write an abbreviated table file.

Before calling this, all parameters and a data destination must be set up.
To produce a pair of files containing abbreviated tables and abbreviated image data, one would proceed as follows:
Initialize JPEG object
Set JPEG parameters
Set destination to table file
jpeg_write_tables();
Set destination to image file
jpeg_start_compress(false);
Write data...
jpeg_finish_compress();

jpeg_write_tables has the side effect of marking all tables written (same as jpeg_suppress_tables(true)). Thus a subsequent jpeg_start_compress will not re-emit the tables unless it is passed write_all_tables=true.

Define a Huffman table

Support routine: generate one scan for specified component

Support routine: generate interleaved DC scan if possible, else N scans

Support routine: generate one scan for each component

Do computations that are needed before master selection phase

Initialization of a JPEG compression object

Initialize main buffer controller.

Initialize master compression control.

Master selection of compression modules. This is done once at the start of processing an image. We determine which modules will be used and give them appropriate initialization calls. This routine is in charge of selecting the modules to be executed and making an initialization call to each one.

Set up the standard Huffman tables (cf. JPEG standard section K.3) IMPORTANT: these are only valid for 8-bit data precision!

Master selection of compression modules for transcoding.

Verify that the scan script in scan_info[] is valid; also determine whether it uses progressive JPEG, and set progressive_mode.