/*

 * Copyright (c) 2016, Oracle and/or its affiliates. All rights reserved.

 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

 *

 * This code is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License version 2 only, as

 * published by the Free Software Foundation.

 *

 * This code 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 General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

 * or visit www.oracle.com if you need additional information or have any

 * questions.

 */

/*

 * @test

 * @bug 8015070

 * @summary Tests for artifacts around the edges of anti-aliased text

 *          drawn over translucent background color.

 */

import java.awt.Color;

import java.awt.Font;

import java.awt.Graphics2D;

import java.awt.RenderingHints;

import java.awt.image.BufferedImage;

import java.io.IOException;

public class AntialiasedTextArtifact {

    /* Image dimensions */

    private static final int TEST_IMAGE_WIDTH  = 2800;

    private static final int TEST_IMAGE_HEIGHT = 100;

    private static final String TEST_STRING    =

        "The quick brown fox jumps over the lazy dog. 0123456789.";

    /*

     * The artifacts appear when text is drawn ontop of translucent

     * background. In other words, a background with alpha channel.

     * Hence we test the algorithm for image types that contain either

     * straight alpha channel or pre-multiplied alpha channel. In

     * addition we test the images with other common pixel formats.

     */

    private static final int[] TYPES = {BufferedImage.TYPE_INT_ARGB,

                                        BufferedImage.TYPE_INT_ARGB_PRE,

                                        BufferedImage.TYPE_4BYTE_ABGR,

                                        BufferedImage.TYPE_4BYTE_ABGR_PRE,

                                        BufferedImage.TYPE_INT_RGB,

                                        BufferedImage.TYPE_INT_BGR,

                                        BufferedImage.TYPE_3BYTE_BGR};

    public static void main(String[] args) throws IOException {

        /* Iterate over different image types */

        for (int type : TYPES) {

            BufferedImage testImg = getBufferedImage(type);

            /* Draw anti-aliased string and check for artifacts */

            drawAntialiasedString(testImg);

            checkArtifact(testImg);

        }

    }

    private static BufferedImage getBufferedImage(int imageType) {

        /* Create a Graphics2D object from the given image type */

        BufferedImage image = new BufferedImage(TEST_IMAGE_WIDTH,

                                                TEST_IMAGE_HEIGHT,

                                                imageType);

        return image;

    }

    private static void drawAntialiasedString(BufferedImage image) {

        /* Create Graphics2D object */

        Graphics2D graphics = (Graphics2D) image.getGraphics();

        /* Fill the image with translucent color */

        graphics.setColor(new Color(127, 127, 127, 127));

        graphics.fillRect(0, 0, TEST_IMAGE_WIDTH, TEST_IMAGE_HEIGHT);

        /* Drawstring with Antialiasing hint */

        graphics.setRenderingHint(RenderingHints.KEY_TEXT_ANTIALIASING,

                                  RenderingHints.VALUE_TEXT_ANTIALIAS_ON);

        Font font = new Font("Verdana" , Font.PLAIN, 60);

        graphics.setFont(font);

        graphics.setColor(new Color(255, 0, 0));

        graphics.drawString(TEST_STRING, 10, 75);

        graphics.dispose();

    }

    private static void checkArtifact(BufferedImage image) throws IOException {

        int componentMask   = 0xff;

        int colorThreshold  = 200;

        int rowIndex = 0;

        int colIndex = 0;

        /* Loop through every pixel to check for possible artifact */

        for (rowIndex = 0; rowIndex < image.getHeight(); rowIndex++) {

            for (colIndex = 0; colIndex < image.getWidth(); colIndex++) {

                /*

                 * API: getRGB(x,y) returns color in INT_ARGB color space.

                 * Extract individual color components with a simple mask.

                 */

                int colorValue = image.getRGB(colIndex, rowIndex);

                int colorComponent1 = colorValue & componentMask;

                int colorComponent2 = (colorValue>>8) & componentMask;

                int colorComponent3 = (colorValue>>16) & componentMask;

                /*

                 * Artifacts are predominantly a subjective decision based on

                 * the quality of the rendered image content. However, in the

                 * current use-case, the artifacts around the edges of the anti

                 * aliased text appear like spots of white pixels without any

                 * relation to the color of foreground text or the background

                 * translucent shape.

                 *

                 * To identify the artifact pixels, each color component from

                 * the testImage is compared with a constant threshold. The

                 * component threshold has been set based on observation from

                 * different experiments on mulitple Java versions.

                 */

                if (colorComponent1 >= colorThreshold

                        && colorComponent2 >= colorThreshold

                        && colorComponent3 >= colorThreshold) {

                    /* Artifact has been noticed. Report error. */

                    throw new RuntimeException("Test Failed.");

                }

            }

        }

    }

}