WarpPI/teavm/src/main/java/ar/com/hjg/pngj/Deinterlacer.java

package ar.com.hjg.pngj;

public class Deinterlacer {
	final ImageInfo imi;
	private int pass; // 1-7
	private int rows, cols;
	int dY, dX, oY, oX; // current step and offset (in pixels)
	int oXsamples, dXsamples; // step in samples

	// current row in the virtual subsampled image; this increments (by 1) from 0 to rows/dy 7 times
	private int currRowSubimg;
	// in the real image, this will cycle from 0 to im.rows in different steps, 7 times
	private int currRowReal;
	private int currRowSeq; // not counting empty rows

	int totalRows;
	private boolean ended = false;

	public Deinterlacer(final ImageInfo iminfo) {
		imi = iminfo;
		pass = 0;
		currRowSubimg = -1;
		currRowReal = -1;
		currRowSeq = 0;
		ended = false;
		totalRows = 0; // lazy compute
		setPass(1);
		setRow(0);
	}

	/** this refers to the row currRowSubimg */
	private void setRow(final int n) { // This should be called only intercally, in sequential order
		currRowSubimg = n;
		currRowReal = n * dY + oY;
		if (currRowReal < 0 || currRowReal >= imi.rows)
			throw new PngjExceptionInternal("bad row - this should not happen");
	}

	/** Skips passes with no rows. Return false is no more rows */
	boolean nextRow() {
		currRowSeq++;
		if (rows == 0 || currRowSubimg >= rows - 1) { // next pass
			if (pass == 7) {
				ended = true;
				return false;
			}
			setPass(pass + 1);
			if (rows == 0) {
				currRowSeq--;
				return nextRow();
			}
			setRow(0);
		} else
			setRow(currRowSubimg + 1);
		return true;
	}

	boolean isEnded() {
		return ended;
	}

	void setPass(final int p) {
		if (pass == p)
			return;
		pass = p;
		final byte[] pp = Deinterlacer.paramsForPass(p);// dx,dy,ox,oy
		dX = pp[0];
		dY = pp[1];
		oX = pp[2];
		oY = pp[3];
		rows = imi.rows > oY ? (imi.rows + dY - 1 - oY) / dY : 0;
		cols = imi.cols > oX ? (imi.cols + dX - 1 - oX) / dX : 0;
		if (cols == 0)
			rows = 0; // well, really...
		dXsamples = dX * imi.channels;
		oXsamples = oX * imi.channels;
	}

	static byte[] paramsForPass(final int p) {// dx,dy,ox,oy
		switch (p) {
			case 1:
				return new byte[] { 8, 8, 0, 0 };
			case 2:
				return new byte[] { 8, 8, 4, 0 };
			case 3:
				return new byte[] { 4, 8, 0, 4 };
			case 4:
				return new byte[] { 4, 4, 2, 0 };
			case 5:
				return new byte[] { 2, 4, 0, 2 };
			case 6:
				return new byte[] { 2, 2, 1, 0 };
			case 7:
				return new byte[] { 1, 2, 0, 1 };
			default:
				throw new PngjExceptionInternal("bad interlace pass" + p);
		}
	}

	/**
	 * current row number inside the "sub image"
	 */
	int getCurrRowSubimg() {
		return currRowSubimg;
	}

	/**
	 * current row number inside the "real image"
	 */
	int getCurrRowReal() {
		return currRowReal;
	}

	/**
	 * current pass number (1-7)
	 */
	int getPass() {
		return pass;
	}

	/**
	 * How many rows has the current pass?
	 **/
	int getRows() {
		return rows;
	}

	/**
	 * How many columns (pixels) are there in the current row
	 */
	int getCols() {
		return cols;
	}

	public int getPixelsToRead() {
		return getCols();
	}

	public int getBytesToRead() { // not including filter byte
		return (imi.bitspPixel * getPixelsToRead() + 7) / 8;
	}

	public int getdY() {
		return dY;
	}

	/*
	 * in pixels
	 */
	public int getdX() {
		return dX;
	}

	public int getoY() {
		return oY;
	}

	/*
	 * in pixels
	 */
	public int getoX() {
		return oX;
	}

	public int getTotalRows() {
		if (totalRows == 0)
			for (int p = 1; p <= 7; p++) {
				final byte[] pp = Deinterlacer.paramsForPass(p); // dx dy ox oy
				final int rows = imi.rows > pp[3] ? (imi.rows + pp[1] - 1 - pp[3]) / pp[1] : 0;
				final int cols = imi.cols > pp[2] ? (imi.cols + pp[0] - 1 - pp[2]) / pp[0] : 0;
				if (rows > 0 && cols > 0)
					totalRows += rows;
			}
		return totalRows;
	}

	/**
	 * total unfiltered bytes in the image, including the filter byte
	 */
	public long getTotalRawBytes() { // including the filter byte
		long bytes = 0;
		for (int p = 1; p <= 7; p++) {
			final byte[] pp = Deinterlacer.paramsForPass(p); // dx dy ox oy
			final int rows = imi.rows > pp[3] ? (imi.rows + pp[1] - 1 - pp[3]) / pp[1] : 0;
			final int cols = imi.cols > pp[2] ? (imi.cols + pp[0] - 1 - pp[2]) / pp[0] : 0;
			final int bytesr = (imi.bitspPixel * cols + 7) / 8; // without filter byte
			if (rows > 0 && cols > 0)
				bytes += rows * (1 + (long) bytesr);
		}
		return bytes;
	}

	public int getCurrRowSeq() {
		return currRowSeq;
	}

}