71 lines
2.2 KiB
Java
71 lines
2.2 KiB
Java
package a2geek.apple2.image.encoder.encode;
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import java.io.ByteArrayOutputStream;
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import a2geek.apple2.image.encoder.A2Image;
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public abstract class A2Encoder {
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private ByteArrayOutputStream encodedData = new ByteArrayOutputStream();
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public abstract void encode(A2Image a2image, int maxSize);
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public abstract String getTitle();
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public void reset(int maxSize) {
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encodedData.reset();
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}
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public void addByte(int value) {
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encodedData.write(value & 0xff);
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}
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public void addBytes(int[] bytes) {
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for (int b : bytes) {
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addByte(b);
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}
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}
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public int getSize() {
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return encodedData.size();
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}
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public byte[] getData() {
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return encodedData.toByteArray();
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}
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/**
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* Compute the run size of the given byte pattern.
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* Specifically, the number of iterations of the given byte pattern.
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*/
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protected int getRunSize(byte[] data, int start, int runLengthSize, int maxIterations) {
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if (start + runLengthSize >= data.length) return 0;
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byte[] run = new byte[runLengthSize];
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System.arraycopy(data, start, run, 0, runLengthSize);
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int runLength = 0;
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for (int i=0; start+i<data.length && runLength<maxIterations; i+= runLengthSize) {
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for (int j=0; j<runLengthSize; j++) {
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int pos = start+i+j;
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if (pos >= data.length) return runLength;
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int byt = data[pos];
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if (run[j] != byt) return runLength;
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}
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runLength++;
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}
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return runLength;
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}
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/**
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* Find the best run of bytes with varying lengths.
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*/
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protected int[] findBestRun(byte[] data, int maxRunSize, int position, int maxRunLength, int bytesUsedFactor) {
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int maxBytesSaved = 0; // We don't want to encode unless we save some space!!
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int bestRunLength = Integer.MIN_VALUE;
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int[] run = null;
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for (int s=0; s<maxRunSize; s++) {
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int runSize = s+1;
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int runLength = getRunSize(data, position, runSize, maxRunLength);
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int bytesUsed = bytesUsedFactor + runSize;
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int bytesSaved = (runLength*runSize) - bytesUsed;
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if (bytesSaved > maxBytesSaved) {
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maxBytesSaved = bytesSaved;
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bestRunLength = runLength;
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run = new int[runSize];
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for (int j=0; j<run.length; j++) run[j]= data[position+j];
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}
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}
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return bestRunLength > 1 ? run : null;
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}
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}
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