50 lines
2.0 KiB
HTML
50 lines
2.0 KiB
HTML
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<html>
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<body bgcolor="white">
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<p>
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PNGJ main package
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</p>
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<p>
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Users of this library should rarely need more than the public members of this package.<br>
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Newcomers: start with <a href="PngReader.html">PngReader</a> and <a href="PngWriter.html">PngWriter</a>.
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</p>
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<p>
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Example of use: this code reads a true colour PNG image (RGB8 or RGBA8)
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and reduces the red channel by half, increasing the green by 20.
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It copies all the "safe" metadata from the original image, and adds a textual metadata.
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<pre class="code">
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public static void convert(String origFilename, String destFilename) {
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// you can also use PngReader (esentially the same) or PngReaderByte
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PngReaderInt pngr = new PngReaderInt(new File(origFilename));
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System.out.println(pngr.toString());
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int channels = pngr.imgInfo.channels;
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if (channels < 3 || pngr.imgInfo.bitDepth != 8)
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throw new RuntimeException("For simplicity this supports only RGB8/RGBA8 images");
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// writer with same image properties as original
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PngWriter pngw = new PngWriter(new File(destFilename), pngr.imgInfo, true);
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// instruct the writer to grab all ancillary chunks from the original
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pngw.copyChunksFrom(pngr.getChunksList(), ChunkCopyBehaviour.COPY_ALL_SAFE);
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// add a textual chunk to writer
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pngw.getMetadata().setText(PngChunkTextVar.KEY_Description, "Decreased red and increased green");
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// also: while(pngr.hasMoreRows())
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for (int row = 0; row < pngr.imgInfo.rows; row++) {
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ImageLineInt l1 = pngr.readRowInt(); // each element is a sample
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int[] scanline = l1.getScanline(); // to save typing
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for (int j = 0; j < pngr.imgInfo.cols; j++) {
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scanline[j * channels] /= 2;
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scanline[j * channels + 1] = ImageLineHelper.clampTo_0_255(scanline[j * channels + 1] + 20);
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}
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pngw.writeRow(l1);
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}
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pngr.end(); // it's recommended to end the reader first, in case there are trailing chunks to read
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pngw.end();
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}
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</pre>
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For more examples, see the tests and samples.
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</p>
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</body>
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</html>
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