|
|||||||||
| Home >> All >> org >> websody >> [ util overview ] | PREV CLASS NEXT CLASS | ||||||||
SUMMARY:  JAVADOC |  SOURCE |  DOWNLOAD | NESTED | FIELD | CONSTR | METHOD |
DETAIL: FIELD | CONSTR | METHOD | ||||||||
org.websody.util
Class ImageInfo
java.lang.Objectorg.websody.util.ImageInfo
- public class ImageInfo
- extends java.lang.Object
Allows basic information about a graphic file to be obtained without the overhead of instanciating an image object. This is particularly valuable for servlets and other programs which may not have access to a graphics context, but which may need dimensions etc. to calculate page layout etc. Note that the filename supplied must be accessible to the program, since the file must be partially read.
| Field Summary | |
protected java.lang.String |
encoding
|
protected java.lang.String |
errorMessage
|
protected int |
format
|
static int |
GIF
|
protected short |
height
|
static int |
JPEG
|
static int |
MAX_HEADER_SIZE
|
protected java.io.InputStream |
stream
|
static int |
UNKNOWN_FORMAT
|
protected short |
width
|
| Constructor Summary | |
protected |
ImageInfo(java.io.InputStream stream)
To obtain information about images use the factory methods above. |
protected |
ImageInfo(java.io.InputStream stream,
int format)
To obtain information about images use the factory methods above. |
| Method Summary | |
protected void |
decodeGifHeader()
Reads the first 13 bytes from a GIF file, and interprets it according to the following rules. |
protected void |
decodeHeader()
Looks for a GIF header, if no valid header is found this method looks for a JPEG header. |
protected void |
decodeJpegHeader()
Retrieves information on JPG images, according to ISO standard 10918-1 and CCITT T.81. |
java.lang.String |
getEncoding()
|
java.lang.String |
getErrorMessage()
|
int |
getFormat()
|
static ImageInfo |
getGifInfo(java.io.InputStream stream)
ImageInfo factory for GIF images |
short |
getHeight()
|
static ImageInfo |
getImageInfo(java.io.InputStream stream)
ImageInfo factory for GIF or JPEG images. |
static ImageInfo |
getJpegInfo(java.io.InputStream stream)
ImageInfo factory for JPEG images |
short |
getWidth()
|
protected short |
shortBigEndian(byte firstRead,
byte lastRead)
Converts bytes in big-endian order to a short |
protected short |
shortLittleEndian(byte firstRead,
byte lastRead)
Converts bytes in little-endian order to a short |
| Methods inherited from class java.lang.Object |
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
| Field Detail |
UNKNOWN_FORMAT
public static final int UNKNOWN_FORMAT
- See Also:
- Constant Field Values
GIF
public static final int GIF
- See Also:
- Constant Field Values
JPEG
public static final int JPEG
- See Also:
- Constant Field Values
MAX_HEADER_SIZE
public static final int MAX_HEADER_SIZE
- See Also:
- Constant Field Values
stream
protected java.io.InputStream stream
format
protected int format
height
protected short height
width
protected short width
encoding
protected java.lang.String encoding
errorMessage
protected java.lang.String errorMessage
| Constructor Detail |
ImageInfo
protected ImageInfo(java.io.InputStream stream)
- To obtain information about images use the factory methods above.
ImageInfo
protected ImageInfo(java.io.InputStream stream, int format)
- To obtain information about images use the factory methods above.
| Method Detail |
getImageInfo
public static ImageInfo getImageInfo(java.io.InputStream stream)
- ImageInfo factory for GIF or JPEG images.
getGifInfo
public static ImageInfo getGifInfo(java.io.InputStream stream)
- ImageInfo factory for GIF images
getJpegInfo
public static ImageInfo getJpegInfo(java.io.InputStream stream)
- ImageInfo factory for JPEG images
decodeHeader
protected void decodeHeader()
throws java.io.IOException
- Looks for a GIF header, if no valid header is found this method looks
for a JPEG header. Useful if the content type is unknown.
decodeGifHeader
protected void decodeGifHeader()
throws java.io.IOException
- Reads the first 13 bytes from a GIF file, and interprets it according to the
following rules.
Bytes 1-3 FILE TYPE = Should be "GIF" for all valid GIF files. Bytes 4-6 ENCODING = '87a' or '89a' at this point in time. Bytes 7-13 SCREEN DESCRIPTOR
The Screen Descriptor describes the overall parameters for all GIF images following. It defines the overall dimensions of the image space or logical screen required, the existance of color mapping information, background screen color, and color depth information. This information is stored in a series of 8-bit bytes as described below.
bits 7 6 5 4 3 2 1 0 Byte # +---------------+ | | 1 +-Screen Width -+ Raster width in pixels (LSB first) | | 2 +---------------+ | | 3 +-Screen Height-+ Raster height in pixels (LSB first) | | 4 +-+-----+-+-----+ M = 1, Global color map follows Descriptor |M| cr |0|pixel| 5 cr+1 = # bits of color resolution +-+-----+-+-----+ pixel+1 = # bits/pixel in image | background | 6 background=Color index of screen background +---------------+ (color is defined from the Global color |0 0 0 0 0 0 0 0| 7 map or default map if none specified) +---------------+
decodeJpegHeader
protected void decodeJpegHeader()
throws java.io.IOException
- Retrieves information on JPG images, according to ISO standard 10918-1
and CCITT T.81.
shortBigEndian
protected short shortBigEndian(byte firstRead,
byte lastRead)
- Converts bytes in big-endian order to a short
shortLittleEndian
protected short shortLittleEndian(byte firstRead,
byte lastRead)
- Converts bytes in little-endian order to a short
getFormat
public int getFormat()
getEncoding
public java.lang.String getEncoding()
getHeight
public short getHeight()
getWidth
public short getWidth()
getErrorMessage
public java.lang.String getErrorMessage()
|
|||||||||
| Home >> All >> org >> websody >> [ util overview ] | PREV CLASS NEXT CLASS | ||||||||
|
SUMMARY: JAVADOC | SOURCE | DOWNLOAD | NESTED | FIELD | CONSTR | METHOD |
DETAIL: FIELD | CONSTR | METHOD | ||||||||