# RadialShadingContext.java

    /*
     * Licensed to the Apache Software Foundation (ASF) under one or more
     * contributor license agreements.  See the NOTICE file distributed with
     * this work for additional information regarding copyright ownership.
     * The ASF licenses this file to You under the Apache License, Version 2.0
     * (the "License"); you may not use this file except in compliance with
     * the License.  You may obtain a copy of the License at
     *
     *      http://www.apache.org/licenses/LICENSE-2.0
     *
     * Unless required by applicable law or agreed to in writing, software
     * distributed under the License is distributed on an "AS IS" BASIS,
     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     * See the License for the specific language governing permissions and
     * limitations under the License.
     */
    package org.apache.pdfbox.pdmodel.graphics.shading;

    import java.awt.Rectangle;
    import java.awt.geom.AffineTransform;
    import java.awt.geom.NoninvertibleTransformException;
    import java.awt.image.ColorModel;
    import java.awt.image.Raster;
    import java.awt.image.WritableRaster;
    import java.io.IOException;
    import org.apache.commons.logging.Log;
    import org.apache.commons.logging.LogFactory;
    import org.apache.pdfbox.cos.COSArray;
    import org.apache.pdfbox.cos.COSBoolean;
    import org.apache.pdfbox.pdmodel.common.function.PDFunction;
    import org.apache.pdfbox.util.Matrix;

    /**
     * AWT PaintContext for radial shading.
     *
     * Performance improvement done as part of GSoC2014, Tilman Hausherr is the mentor.
     *
     * @author Shaola Ren
     */
    public class RadialShadingContext extends ShadingContext
    {
        private static final Log LOG = LogFactory.getLog(RadialShadingContext.class);

        private PDShadingType3 radialShadingType;

        private final float[] coords;
        private final float[] domain;
        private final boolean[] extend;
        private final double x1x0;
        private final double y1y0;
        private final double r1r0;
        private final double r0pow2;
        private final float d1d0;
        private final double denom;

        private final int factor;
        private final int[] colorTable;

        private AffineTransform rat;

        /**
         * Constructor creates an instance to be used for fill operations.
         *
         * @param shading the shading type to be used
         * @param colorModel the color model to be used
         * @param xform transformation for user to device space
         * @param matrix the pattern matrix concatenated with that of the parent content stream
         * @param deviceBounds the bounds of the area to paint, in device units
         * @throws IOException if there is an error getting the color space or doing color conversion.
         */
        public RadialShadingContext(PDShadingType3 shading, ColorModel colorModel,
                                    AffineTransform xform, Matrix matrix, Rectangle deviceBounds)
                                    throws IOException
        {
            super(shading, colorModel, xform, matrix);
            this.radialShadingType = shading;
            coords = shading.getCoords().toFloatArray();

            // domain values
            if (this.radialShadingType.getDomain() != null)
            {
                domain = shading.getDomain().toFloatArray();
            }
            else
            {
                // set default values
                domain = new float[] { 0, 1 };
            }

            // extend values
            COSArray extendValues = shading.getExtend();
            if (extendValues != null)
            {
                extend = new boolean[2];
                extend[0] = ((COSBoolean) extendValues.getObject(0)).getValue();
                extend[1] = ((COSBoolean) extendValues.getObject(1)).getValue();
            }
            else
            {
                // set default values
                extend = new boolean[] { false, false };
            }
            // calculate some constants to be used in getRaster
            x1x0 = coords[3] - coords[0];
            y1y0 = coords[4] - coords[1];
            r1r0 = coords[5] - coords[2];
            r0pow2 = Math.pow(coords[2], 2);
            denom = Math.pow(x1x0, 2) + Math.pow(y1y0, 2) - Math.pow(r1r0, 2);
            d1d0 = domain[1] - domain[0];

            try
            {
                // get inverse transform to be independent of current user / device space
                // when handling actual pixels in getRaster()
                rat = matrix.createAffineTransform().createInverse();
                rat.concatenate(xform.createInverse());
            }
            catch (NoninvertibleTransformException ex)
            {
                LOG.error(ex.getMessage() + ", matrix: " + matrix, ex);
                rat = new AffineTransform();
            }

            // shading space -> device space
            AffineTransform shadingToDevice = (AffineTransform)xform.clone();
            shadingToDevice.concatenate(matrix.createAffineTransform());

            // worst case for the number of steps is opposite diagonal corners, so use that
            double dist = Math.sqrt(Math.pow(deviceBounds.getMaxX() - deviceBounds.getMinX(), 2) +
                                    Math.pow(deviceBounds.getMaxY() - deviceBounds.getMinY(), 2));
            factor = (int) Math.ceil(dist);

            // build the color table for the given number of steps
            colorTable = calcColorTable();
        }

        /**
         * Calculate the color on the line that connects two circles' centers and store the result in an
         * array.
         *
         * @return an array, index denotes the relative position, the corresponding value the color
         */
        private int[] calcColorTable() throws IOException
        {
            int[] map = new int[factor + 1];
            if (factor == 0 || Float.compare(d1d0,0) == 0)
            {
                float[] values = radialShadingType.evalFunction(domain[0]);
                map[0] = convertToRGB(values);
            }
            else
            {
                for (int i = 0; i <= factor; i++)
                {
                    float t = domain[0] + d1d0 * i / factor;
                    float[] values = radialShadingType.evalFunction(t);
                    map[i] = convertToRGB(values);
                }
            }
            return map;
        }

        @Override
        public void dispose()
        {
            super.dispose();
            radialShadingType = null;
        }

        @Override
        public Raster getRaster(int x, int y, int w, int h)
        {
            // create writable raster
            WritableRaster raster = getColorModel().createCompatibleWritableRaster(w, h);
            float inputValue = -1;
            boolean useBackground;
            int[] data = new int[w * h * 4];
            float[] values = new float[2];
            for (int j = 0; j < h; j++)
            {
                for (int i = 0; i < w; i++)
                {
                    values[0] = x + i;
                    values[1] = y + j;
                    rat.transform(values, 0, values, 0, 1);
                    useBackground = false;
                    float[] inputValues = calculateInputValues(values[0], values[1]);
                    if (Float.isNaN(inputValues[0]) && Float.isNaN(inputValues[1]))
                    {
                        if (getBackground() == null)
                        {
                            continue;
                        }
                        useBackground = true;
                    }
                    else
                    {
                        // choose 1 of the 2 values
                        if (inputValues[0] >= 0 && inputValues[0] <= 1)
                        {
                            // both values are in the range -> choose the larger one
                            if (inputValues[1] >= 0 && inputValues[1] <= 1)
                            {
                                inputValue = Math.max(inputValues[0], inputValues[1]);
                            }
                            // first value is in the range, the second not -> choose first value
                            else
                            {
                                inputValue = inputValues[0];
                            }
                        }
                        else
                        {
                            // first value is not in the range,
                            // but the second -> choose second value
                            if (inputValues[1] >= 0 && inputValues[1] <= 1)
                            {
                                inputValue = inputValues[1];
                            }
                            // both are not in the range
                            else
                            {
                                if (extend[0] && extend[1])
                                {
                                    inputValue = Math.max(inputValues[0], inputValues[1]);
                                }
                                else if (extend[0])
                                {
                                    inputValue = inputValues[0];
                                }
                                else if (extend[1])
                                {
                                    inputValue = inputValues[1];
                                }
                                else if (getBackground() != null)
                                {
                                    useBackground = true;
                                }
                                else
                                {
                                    continue;
                                }
                            }
                        }
                        // input value is out of range
                        if (inputValue > 1)
                        {
                            // extend shading if extend[1] is true and nonzero radius
                            if (extend[1] && coords[5] > 0)
                            {
                                inputValue = 1;
                            }
                            else
                            {
                                if (getBackground() == null)
                                {
                                    continue;
                                }
                                useBackground = true;
                            }
                        }
                        // input value is out of range
                        else if (inputValue < 0)
                        {
                            // extend shading if extend[0] is true and nonzero radius
                            if (extend[0] && coords[2] > 0)
                            {
                                inputValue = 0;
                            }
                            else
                            {
                                if (getBackground() == null)
                                {
                                    continue;
                                }
                                useBackground = true;
                            }
                        }
                    }
                    int value;
                    if (useBackground)
                    {
                        // use the given background color values
                        value = getRgbBackground();
                    }
                    else
                    {
                        int key = (int) (inputValue * factor);
                        value = colorTable[key];
                    }
                    int index = (j * w + i) * 4;
                    data[index] = value & 255;
                    value >>= 8;
                    data[index + 1] = value & 255;
                    value >>= 8;
                    data[index + 2] = value & 255;
                    data[index + 3] = 255;
                }
            }
            raster.setPixels(0, 0, w, h, data);
            return raster;
        }

        private float[] calculateInputValues(double x, double y)
        {
            // According to Adobes Technical Note #5600 we have to do the following
            //
            // x0, y0, r0 defines the start circle x1, y1, r1 defines the end circle
            //
            // The parametric equations for the center and radius of the gradient fill circle moving
            // between the start circle and the end circle as a function of s are as follows:
            //
            // xc(s) = x0 + s * (x1 - x0) yc(s) = y0 + s * (y1 - y0) r(s) = r0 + s * (r1 - r0)
            //
            // Given a geometric coordinate position (x, y) in or along the gradient fill, the
            // corresponding value of s can be determined by solving the quadratic constraint equation:
            //
            // [x - xc(s)]2 + [y - yc(s)]2 = [r(s)]2
            //
            // The following code calculates the 2 possible values of s
            //
            double p = -(x - coords[0]) * x1x0 - (y - coords[1]) * y1y0 - coords[2] * r1r0;
            double q = (Math.pow(x - coords[0], 2) + Math.pow(y - coords[1], 2) - r0pow2);
            double root = Math.sqrt(p * p - denom * q);
            float root1 = (float) ((-p + root) / denom);
            float root2 = (float) ((-p - root) / denom);
            if (denom < 0)
            {
                return new float[] { root1, root2 };
            }
            else
            {
                return new float[] { root2, root1 };
            }
        }

        /**
         * Returns the coords values.
         */
        public float[] getCoords()
        {
            return coords;
        }

        /**
         * Returns the domain values.
         */
        public float[] getDomain()
        {
            return domain;
        }

        /**
         * Returns the extend values.
         */
        public boolean[] getExtend()
        {
            return extend;
        }

        /**
         * Returns the function.
         *
         * @throws java.io.IOException if we were not able to create the function.
         */
        public PDFunction getFunction() throws IOException
        {
            return radialShadingType.getFunction();
        }
    }