1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
|
Copyright (c) 1998,1999 Six-Legged Software
All rights reserved.
README - com.sixlegs.image.png v1.0
Features
Supports all valid bit depths (grayscale/color), interlacing, paletted
images, alpha channel/transparency, gamma correction, access to most
standard chunks, private chunk handling, and progressive display.
Revision History
Changes from v0.9 -> v1.0:
* Released as open-source under LGPL.
* Workaround for IE4.0, should work fine now.
Changes from v0.8 -> v0.9:
* Changes to significantly reduce memory usage (up to 40%):
+ "setViewingGammaLocal", "setDisplayGammaLocal" methods removed.
+ Multiple productions of image data no longer supported.
+ Call "getEverything" only when you do not need image data.
* Support for proposed iTXt chunk (TextChunk class).
* "getTextChunk" now returns a TextChunk instead of String.
* "getTextKeys" changed to "getTextChunks".
* CR, LF, and CR-LF combinations in text chunks are transformed
to local newline conventions.
* Standard text chunks keywords are now case-sensitive.
* Character codes 0-8,11,12,14-31,127-159 in text chunks are
displayed using octal "\nnn" notation.
Changes from v0.7 -> v0.8:
* Support for oFFs, pCAL, sBIT, sCAL, and sPLT chunks.
* ChunkHandlers can now override standard ancillary chunks.
* Added documentation on reducing distribution size (see below).
* Fixed bug with getProperty("background").
* Fixed bug with getProperty("time").
* Modest performance improvements.
* Changed some property names and constants for consistency.
* Added source files for each example class.
Changes from v0.6 -> v0.7:
* Added getProperty method for easy access to chunk data.
* Added ChunkHandler interface for private chunk handling.
* Support for sRGB and iCCP chunks.
* Removed PngHeader class. Equivalent methods are now in PngImage.
* Improved text chunk handling.
* Changed "setViewingGamma" and "setDisplayGamma" to
"setViewingExponent" and "setDisplayExponent" to reflect proposed
changes to the PNG specification.
* Added GrayscaleFilter class (getGrayscaleFilter method removed).
* Example code documentation.
Changes from v0.5 -> v0.6:
* Progressive display of interlaced images.
* Grayscale filtering.
* "setViewingGammaLocal" and "setDisplayGammaLocal" allow you to
override the default gamma settings for an image.
* Added a RemoveAlphaFilter example class for better display
of transparent images.
* Fixed a bug with 16-bit grayscale images with bKGD chunks.
* Fixed a bug with very small interlaced images.
* Fixed a possible bug with interlaced images in which the first
scanline of each pass did not use the Sub or None filter.
* Package has changed from com.sixlegs.PNG to com.sixlegs.image.png;
this is the final package name.
* More documentation.
Requirements
This package uses the java.util.zip package for ZLIB decompression,
and so requires Java 1.1 or higher. This means that it will not work
in older browsers, such as Netscape 3.x. It has been tested in
Netscape Communicator under Windows NT. Let me know if you encounter
problems on platforms that supposedly support Java 1.1.
Getting Started
The entire com.sixlegs.PNG package has been archived in the png.jar
file. The easiest way to start using the package is to simply include
the path to the jar file in your CLASSPATH environment variable.
Alternatively, you can extract the class files by running the command
jar xvf png.jar
You would still probably want to add the location of the extracted
files to your CLASSPATH.
Using the Package
Usually you will 'import com.sixlegs.image.png.*;' at the beginning
of your code. The PngImage class is an ImageProducer, so getting an
Image object from a local PNG file is easy:
PngImage png = new PngImage("test.png");
Image img = Toolkit.getDefaultToolkit().createImage(png);
The PngImage object also has constructors to read from a URL or an
InputStream. In addition, you can set variables, such as gamma
parameters, that will affect the resulting image. See the
documentation located in the 'doc' directory for more details.
Example code is located in the 'examples' directory.
Reducing distribution size
Not all of the class files in the library are critical. By removing
unnecessary classes you can reduce the total size of the jar file
by almost half.
Each chunk type has its own class. The only five that must be
included are IHDR, IDAT, IEND, PLTE, and tRNS. All others may be
safely removed.
Be aware that the removal of certain chunks classes, such as gAMA,
sRGB, and bKGD, may affect the displayed image.
Furthermore, there is a separate "BitMover" class for each image
color format. You may safely remove the formats that you *know* you
do not need to support. Here is a key to the BitMover classes:
BitMover1G - 1 bit grayscale
BitMover1P - 1 bit paletted
BitMover2G - 2 bit grayscale
BitMover2P - 2 bit paletted
BitMover4G - 4 bit grayscale
BitMover4P - 4 bit paletted
BitMover8G - 8 bit grayscale
BitMover8GA - 8 bit grayscale + 8 bit alpha
BitMover8P - 8 bit paletted
BitMover8RGB - 24 bit truecolor
BitMover8RGBA - 24 bit truecolor + 8 bit alpha
BitMover16G - 16 bit grayscale
BitMover16GA - 16 bit grayscale + 16 bit alpha
BitMover16RGB - 48 bit truecolor
BitMover16RGBA - 48 bit truecolor + 16 bit alpha
Miscellaneous:
* Remove KeyValueChunk only if you remove AbstractTextChunk and iCCP.
* Remove AbstractTextChunk only if you remove tEXt, zTXt, and iTXt.
* Remove VcHRM only if you remove sRGB and cHRM.
* If you do not need private chunk handling you may remove
UserChunk and ChunkHandler.
Contact Information
The latest version of this package is available from:
http://www.sixlegs.com/png/
Please let me know about any problems you encounter, or features
that you would find valuable.
Chris Nokleberg <chris@sixlegs.com>
|
