pagespeed::image_compression::ScanlineResizer Class Reference

#include "image_resizer.h"

Inheritance diagram for pagespeed::image_compression::ScanlineResizer:

Public Member Functions
	ScanlineResizer (MessageHandler *handler)
bool	Initialize (ScanlineReaderInterface *reader, size_t output_width, size_t output_height)
	Initializes the resizer with a reader and the desired output size.
virtual ScanlineStatus	ReadNextScanlineWithStatus (void **out_scanline_bytes)
virtual bool	Reset ()
	Resets the resizer to its initial state. Always returns true.
virtual size_t	GetBytesPerScanline ()
	Returns number of bytes required to store a scanline.
virtual bool	HasMoreScanLines ()
virtual size_t	GetImageHeight ()
	Returns the height of the image.
virtual size_t	GetImageWidth ()
	Returns the width of the image.
virtual PixelFormat	GetPixelFormat ()
	Returns the pixel format of the image.
virtual bool	IsProgressive ()
	Returns true if the image is encoded in progressive / interlacing format.
virtual ScanlineStatus	InitializeWithStatus (const void *image_buffer, size_t buffer_length)
Public Member Functions inherited from pagespeed::image_compression::ScanlineReaderInterface
bool	Initialize (const void *image_buffer, size_t buffer_length)
bool	ReadNextScanline (void **out_scanline_bytes)

Static Public Attributes
static const size_t	kPreserveAspectRatio = 0

Detailed Description

Class ScanlineResizer resizes an image, and outputs a scanline at a time. To use it, you need to provide an initialized reader implementing ScanlineReaderInterface. The ScanlineResizer object will instruct the reader to fetch the image scanlines required for the resized scanline.

You can specify the width, the height, or both in pixels. If you want to preserve the aspect ratio, you can specify only one of them, and pass in kPreserveAspectRatio for the other one.

Currently, ScanlineResizer only supports shrinking. It works best when the image shrinks significantly, e.g, by more than 2x times.

Member Function Documentation

virtual bool pagespeed::image_compression::ScanlineResizer::HasMoreScanLines ( )

virtual

Returns true if there are more scanlines to read. Returns false if the object has not been initialized or all of the scanlines have been read.

Implements pagespeed::image_compression::ScanlineReaderInterface.

virtual ScanlineStatus pagespeed::image_compression::ScanlineResizer::InitializeWithStatus ( const void *  image_buffer, size_t  buffer_length  )

virtual

This method should not be called. If it does get called, in DEBUG mode it will throw a FATAL error and in RELEASE mode it does nothing.

Implements pagespeed::image_compression::ScanlineReaderInterface.

virtual ScanlineStatus pagespeed::image_compression::ScanlineResizer::ReadNextScanlineWithStatus ( void **  out_scanline_bytes )

virtual

Reads the next available scanline. Returns an error if the next scanline is not available. This can happen when the reader cannot provide enough image rows, or when all of the scanlines have been read.

Implements pagespeed::image_compression::ScanlineReaderInterface.

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The documentation for this class was generated from the following file:

• pagespeed/kernel/image/image_resizer.h