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/*
 * Gray8VertTrapWarp.java
 *
 * Created on September 9, 2006, 3:17 PM
 *
 * Copyright 2007 by Jon A. Webb
 *     This program is free software: you can redistribute it and/or modify
 *    it under the terms of the GNU Lesser General Public License as published by
 *    the Free Software Foundation, either version 3 of the License, or
 *    (at your option) any later version.
 *
 *    This program is distributed in the hope that it will be useful,
 *    but WITHOUT ANY WARRANTY; without even the implied warranty of
 *    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 *    GNU Lesser General Public License for more details.
 *
 *    You should have received a copy of the Lesser GNU General Public License
 *    along with this program.  If not, see .
 *
 */

package com.github.ojil.algorithm;
import com.github.ojil.core.Error;
import com.github.ojil.core.Gray8Image;
import com.github.ojil.core.Image;
import com.github.ojil.core.PipelineStage;

/**
 * This PipelineStage warps a trapezoid in the input gray image into a 
 * rectangular output image. The trapezoid is alined vertically, i.e., the
 * vertical edges are parallel
 * @author webb
 */
public class Gray8VertTrapWarp extends PipelineStage {
   private int nRowTopEnd;
   private int nRowTopStart;
   private int nRowBotEnd;
   private int nRowBotStart;
   private int nColEnd;
   private int nColStart;
   
    
    /** Creates a new instance of Gray8VertTrapWarp. Gray8VertTrapWarp warps a trapezoidal
     * region in an input gray image into a rectangular output image. The
     * left and right sides of the trapezoid are aligned with the columns of the image.
     * 

* The bounds are specified here in a manner consistent with the way they * are specified as array bounds -- that is, the starting bound is closed * (≤) and the ending bound is open (<). * * @param nColStart starting column of trapezoid in input image * @param nColEnd bounding column of trapezoid in input image. This is one past * the actual last column processed in the input image. * @param nRowTopStart top edge of trapezoid in starting column. * @param nRowBotStart bottom bound of trapezoid in starting column. This is * one past the actual last row processed in the input image. * @param nRowTopEnd top edge of trapezoid in ending column * @param nRowBotEnd bottom bound of trapezoid in ending column. This is one * past the actual last column processed in the input image. The column * referred to as the ending row is the one above the bounding row, i.e., * nColEnd. * @throws com.github.ojil.core.Error if the trapezoid is empty or outside * the bounds of any image, i.e., if nColStart < 0, or nColEnd ≤ nColStart, * or nRowTopStart ≤ nRowBotStart, or nRowTopEnd ≤ nRowBotEnd. */ public Gray8VertTrapWarp( int nColStart, int nColEnd, int nRowTopStart, int nRowBotStart, int nRowTopEnd, int nRowBotEnd) throws com.github.ojil.core.Error { setTrapezoid(nColStart, nColEnd, nRowTopStart, nRowBotStart, nRowTopEnd, nRowBotEnd); } /** Returns the left column position of the trapezoid in the ending row. * * @return the left edge position of the trapezoid in the ending row. */ public int getColLeftEnd() { return this.nRowTopEnd; } /** Returns the left column position of the trapezoid in the starting row. * * @return the left edge position of the trapezoid in the starting row. */ public int getColLeftStart() { return this.nRowTopStart; } /** Returns the right column position of the trapezoid in the ending row. * * @return the right edge position of the trapezoid in the ending row. */ public int getColRightEnd() { return this.nRowBotEnd; } /** Returns the right column position of the trapezoid in the starting row. * * @return the right edge position of the trapezoid in the starting row. */ public int getColRightStart() { return this.nRowBotStart; } /** Returns the ending row of the trapezoid. * * @return the bottom row of the trapezoid. */ public int getRowEnd() { return this.nColEnd; } /** Returns the starting row of the trapezoid. * * @return the top row of the trapezoid. */ public int getRowStart() { return this.nColStart; } /** * Warps a trapezoidal region in the input gray image into a rectangular * output image. Uses bilinear interpolation. The calculation of fractional * image coordinates is done by multiplying all the coordinates by 256, * to avoid floating point computation. * * @param image the input gray image. * @throws com.github.ojil.core.Error if the input image is not gray, * or the trapezoid already specified extends outside its bounds. */ public void push(Image image) throws com.github.ojil.core.Error { if (!(image instanceof Gray8Image)) { throw new Error( Error.PACKAGE.ALGORITHM, ErrorCodes.IMAGE_NOT_GRAY8IMAGE, image.toString(), null, null); } if (this.nRowBotStart > image.getHeight() || this.nRowBotEnd > image.getHeight() || this.nColEnd > image.getWidth()) { throw new Error( Error.PACKAGE.CORE, com.github.ojil.core.ErrorCodes.BOUNDS_OUTSIDE_IMAGE, image.toString(), this.toString(), null); } // we scale everything by 8 bits for accurate computation without // floating point int fTop = this.nRowTopStart << 8; int fBot = this.nRowBotStart << 8; int nHeight = imageOutput.getHeight(); int nWidth = imageOutput.getWidth(); int fTopIncr = ((this.nRowTopEnd - this.nRowTopStart) << 8) / nWidth; int fBotIncr = ((this.nRowBotEnd - this.nRowBotStart) << 8) / nWidth; Byte[] in = ((Gray8Image) image).getData(); Byte[] out = ((Gray8Image)super.imageOutput).getData(); for (int i=0; i> 8); int topPixel = in[i+this.nColStart+(iY)*image.getWidth()]; int botPixel = in[i+this.nColStart+(iY+1)*image.getWidth()]; // calculate fractional component of pixel between left and right int interp = ((botPixel - topPixel) * ((fY - (iY << 8))) >> 8); out[i+j*nWidth] = (byte) Math.max( Byte.MIN_VALUE, Math.min( Byte.MAX_VALUE, topPixel + interp)); fY += fYIncr; } fTop += fTopIncr; fBot += fBotIncr; } super.setOutput(super.imageOutput); } /** Sets the bounds of the trapezoid. Recreates the output image when they * change. The output height is set to the input trapezoid height, and the * output width is set to the larger of the trapezoid width at the first * and last rows. * * @param nColStart starting row of trapezoid in input image * @param nColEnd ending row of trapezoid in input image * @param nRowTopStart left edge of trapezoid on starting row. * @param nRowBotStart right edge of trapezoid on starting row * @param nRowTopEnd left edge of trapezoid on ending row * @param nRowBotEnd right edge of trapezoid on ending row * @throws com.github.ojil.core.Error if the trapezoid is empty or outside * the bounds of any image, i.e., if nColStart < 0, or nColEnd ≤ nColStart, * or nRowTopStart ≤ nRowBotStart, or nRowTopEnd ≤ nRowBotEnd. */ public void setTrapezoid( int nColStart, int nColEnd, int nRowTopStart, int nRowBotStart, int nRowTopEnd, int nRowBotEnd) throws com.github.ojil.core.Error { if (nColStart >= nColEnd || nRowTopStart >= nRowBotStart || nRowTopEnd >= nRowBotEnd) { throw new Error( Error.PACKAGE.ALGORITHM, ErrorCodes.PARAMETER_OUT_OF_RANGE, new Integer(nColStart).toString(), new Integer(nColEnd).toString(), null); } this.nColStart = nColStart; this.nColEnd = nColEnd; this.nRowTopStart = nRowTopStart; this.nRowBotStart = nRowBotStart; this.nRowTopEnd = nRowTopEnd; this.nRowBotEnd = nRowBotEnd; if (this.nColStart < 0 || this.nRowTopStart < 0 || this.nRowBotStart < 0) { throw new Error( Error.PACKAGE.CORE, com.github.ojil.core.ErrorCodes.BOUNDS_OUTSIDE_IMAGE, this.toString(), null, null); } int nWidth = this.nColEnd - this.nColStart; int nHeight = Math.max( this.nRowBotStart - this.nRowTopStart, this.nRowBotEnd - this.nRowTopEnd); super.imageOutput = new Gray8Image(nWidth, nHeight); } /** * Returns a string describing the current instance. All the constructor * parameters are returned in the order specified in the constructor. * @return The string describing the current instance. The string is of the form * "jjil.algorithm.Gray8VertTrapWarpxxx (startRow,endRow,leftColStart, * rightColStart,leftColEnd,rightColEnd)" */ public String toString() { return super.toString() + " (" + this.nColStart + "," + //$NON-NLS-1$ //$NON-NLS-2$ this.nColEnd + "," + this.nRowTopStart + "," + //$NON-NLS-1$ //$NON-NLS-2$ this.nRowBotStart + "," + this.nRowTopEnd + "," + //$NON-NLS-1$ //$NON-NLS-2$ this.nRowBotEnd + ")"; //$NON-NLS-1$ } }





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