An interface for bilevel pixel image data classes.
Each pixel in a bilevel image can have two possible values,
BLACK
and
WHITE
.
Those two constants are guaranteed to be
0
and
1
, although
you should not make any assumptions about what value any of the two constants has.
This is the type of image used for faxes.
Black and white photos are usually stored as grayscale images.
Apart from implementing
PixelImage
- like all image data classes in JIU -
this interface is also an
IntegerImage
(each sample is either 0 or 1) and
a
GrayImage
(black and white are both grayscale values).
The combination of
IntegerImage
and
GrayImage
is
GrayIntegerImage
,
which is the direct superinterface of this interface.
Packed bytes
There are methods to get and put
packed bytes in this interface.
A packed byte is a
byte
value that stores eight horizontally neighbored bilevel
pixels in it (pixel and sample can be used interchangeably in the context of bilevel images
because there is only one sample per pixel).
The most significant bit of such a packed bit is defined to be the leftmost of the
eight pixels, the second-most significant bit is the pixel to the right of that leftmost pixel,
and so on. The least significant bit is the rightmost pixel.
If a bit is set, the corresponing pixel value is supposed to be white, otherwise black.
Usage examples
Here are some code examples that demonstrate how to access image data with this class.
BilevelImage image = new MemoryBilevelImage(2000, 500);
// now set all pixels in the first row to white
for (int x = 0; x < image.getWidth(); x++)
{
image.putWhite(x, 0);
}
// put vertical stripes on the rest
for (int y = 1; y < image.getHeight(); y++)
{
for (int x = 0; x < image.getWidth(); x++)
{
int sample;
if ((x % 2) == 0)
{
sample = BilevelImage.BLACK;
}
else
{
sample = BilevelImage.WHITE;
}
image.putSample(x, y, sample);
}
}
getPackedBytes
public void getPackedBytes(int x,
int y,
int numSamples,
byte[] dest,
int destOffset,
int destBitOffset)
Sets a number of samples in the argument array from this image.
x
- horizontal position of first sample of this image to ready
- vertical position of samples to be read from this imagenumSamples
- number of samples to be setdest
- array with packed pixels to which samples are copieddestOffset
- index into dest array of the first byte value to write sample values todestBitOffset
- index of first bit of dest[destOffset]
to write a sample to (0 is leftmost, 1 is second-leftmost up to 7, which is the rightmost)
putPackedBytes
public void putPackedBytes(int x,
int y,
int numSamples,
byte[] src,
int srcOffset,
int srcBitOffset)
Sets a number of samples in the image from the argument array data.
x
- horizontal position of first sample to be sety
- vertical position of samples to be setnumSamples
- number of samples to be setsrc
- array with packed pixels to be setsrcOffset
- index into src array of the first byte value to read sample values fromsrcBitOffset
- index of first bit of src[srcOffset]
to
read a sample from (0 is leftmost, 1 is second-leftmost up to 7, which is the rightmost)