Module org.apache.sis.feature

Package org.apache.sis.image

Class ImageCombiner

Object

ImageCombiner

All Implemented Interfaces:

Consumer<Rendered­Image>

public class ImageCombiner
extends Object
implements Consumer<RenderedImage>

Combines an arbitrary number of images into a single one. The combined images may use different coordinate systems if a resampling operation is specified. The workflow is as below:

1. Creates an Image­Combiner with the destination image where to write.
2. Configure with methods such as set­Interpolation(…).
3. Invoke accept(…) or resample(…) methods for each image to combine.
4. Get the combined image with result().

Images are combined in the order they are specified. If the same pixel is written by many images, then the final value is the pixel of the last image specified. In current implementation, the last pixel values win even if those pixels are transparent (i.e. Image­Combiner does not yet handle alpha values).

Limitations

Current implementation does not try to map source bands to target bands for the same colors. For example, it does not verify if band order needs to be reversed because an image is RGB and the other image is BVR. It is caller responsibility to ensure that bands are in the same order.

Current implementation does not expand the destination image for accommodating any area of a given image that appear outside the destination image bounds. Only the intersection of both images is used.

Since:

1.1

Constructor Summary

Constructors

Constructor	Description
Image­Combiner(Writable­Rendered­Image destination)	Creates an image combiner which will write in the given image.
Image­Combiner(Writable­Rendered­Image destination, Image­Processor processor)	Creates an image combiner which will use the given processor for resampling operations.

Method Summary

Modifier and Type	Method	Description
void	accept(Rendered­Image source)	Writes the given image on top of destination image.
Data­Type	get­Band­Type()	Returns the type of number used for representing the values of each band.
Interpolation	get­Interpolation()	Returns the interpolation method to use during resample operations.
Quantity<?>[]	get­Positional­Accuracy­Hints()	Returns hints about the desired positional accuracy, in "real world" units or in pixel units.
void	resample(Rendered­Image source, Rectangle bounds, Math­Transform to­Source)	Combines the result of resampling the given image.
Rendered­Image	result()	Returns the combination of destination image with all images specified to Image­Combiner methods.
void	set­Interpolation(Interpolation method)	Sets the interpolation method to use during resample operations.
void	set­Positional­Accuracy­Hints(Quantity<?>... hints)	Sets hints about desired positional accuracy, in "real world" units or in pixel units.

Methods inherited from class Object

clone, equals, finalize, get­Class, hash­Code, notify, notify­All, to­String, wait, wait, wait

Methods inherited from interface Consumer

and­Then

Constructor Details

ImageCombiner

public ImageCombiner(WritableRenderedImage destination)

Creates an image combiner which will write in the given image. That image is not cleared; pixels that are not overwritten by calls to the accept(…) or resample(…) methods will be left unchanged.

Parameters:

destination - the image where to combine images.

ImageCombiner

public ImageCombiner(WritableRenderedImage destination,
 ImageProcessor processor)

Creates an image combiner which will use the given processor for resampling operations. The given destination image is not cleared; pixels that are not overwritten by calls to the accept(…) or resample(…) methods will be left unchanged.

Parameters:

destination - the image where to combine images.

processor - the processor to use for resampling operations.

Since:

1.2

Method Details

getInterpolation

public Interpolation getInterpolation()

Returns the interpolation method to use during resample operations.

Returns:

interpolation method to use during resample operations.

See Also:

• resample(Rendered­Image, Rectangle, Math­Transform)

setInterpolation

public void setInterpolation(Interpolation method)

Sets the interpolation method to use during resample operations.

Parameters:

method - interpolation method to use during resample operations.

See Also:

• resample(Rendered­Image, Rectangle, Math­Transform)

getPositionalAccuracyHints

public Quantity<?>[] getPositionalAccuracyHints()

Returns hints about the desired positional accuracy, in "real world" units or in pixel units. If the returned array is non-empty and contains accuracies large enough, Image­Combiner may use some slightly faster algorithms at the expense of accuracy.

Returns:

desired accuracy in no particular order, or an empty array if none.

See Also:

• Image­Processor.get­Positional­Accuracy­Hints()

setPositionalAccuracyHints

public void setPositionalAccuracyHints(Quantity<?>... hints)

Sets hints about desired positional accuracy, in "real world" units or in pixel units. Accuracy can be specified in real world units such as metres or in pixel units, which are converted to real world units depending on image resolution. If more than one value is applicable to a dimension (after unit conversion if needed), the smallest value is taken.

Parameters:

hints - desired accuracy in no particular order, or a null array if none. Null elements in the array are ignored.

See Also:

• Image­Processor.set­Positional­Accuracy­Hints(Quantity...)

getBandType

public DataType getBandType()

Returns the type of number used for representing the values of each band.

Returns:

the type of number capable to hold sample values of each band.

Since:

1.4

accept

public void accept(RenderedImage source)

Writes the given image on top of destination image. The given source image shall use the same pixel coordinate system than the destination image (but not necessarily the same tile indices). For every (x,y) pixel coordinates in the destination image:

• If (x,y) are valid source pixel coordinates, then the source pixel values overwrite the destination pixel values.
• Otherwise the destination pixel is left unchanged.

Note that source pixels overwrite destination pixels even if they are transparent (i.e. Image­Combiner does not yet handle alpha values).

Specified by:

accept in interface Consumer<Rendered­Image>

Parameters:

source - the image to write on top of destination image.

resample

public void resample(RenderedImage source,
 Rectangle bounds,
 MathTransform toSource)

Combines the result of resampling the given image. The resampling operation is defined by a potentially non-linear transform from the destination image to the specified source image. That transform should map pixel centers.

Properties used

This operation uses the following properties in addition to method parameters:

• Interpolation method (nearest neighbor, bilinear, etc).
• Positional accuracy hints for enabling faster resampling at the cost of lower precision.

Contrarily to Image­Processor, this method does not use fill values. Destination pixels that cannot be mapped to source pixels are left unchanged.

Parameters:

source - the image to be resampled.

bounds - domain of pixel coordinates in the destination image, or null for the whole image.

to­Source - conversion of pixel coordinates from destination image to source image.

See Also:

• Image­Processor.resample(Rendered­Image, Rectangle, Math­Transform)

result

public RenderedImage result()

Returns the combination of destination image with all images specified to Image­Combiner methods. This may be the destination image specified at construction time, but may also be a larger image if the destination has been dynamically expanded for accommodating larger sources.

Note: dynamic expansion is not yet implemented in current version. If a future version implements it, we shall guarantee that the coordinate of each pixel is unchanged (i.e. the image min­X and min­Y may become negative, but the pixel identified by coordinates (0,0) for instance will stay the same pixel.)

Returns:

the combination of destination image with all source images.