1 /*
2 * Copyright (c) 2016, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 */
23 import java.awt.Color;
24 import java.awt.Font;
25 import java.awt.Graphics2D;
26 import java.awt.RenderingHints;
27 import java.awt.image.BufferedImage;
28 import java.io.IOException;
29
30 /**
31 * @test
32 * @bug 8015070
33 * @summary Tests for artifacts around the edges of anti-aliased text
34 * drawn over translucent background color.
35 */
36 public class AntialiasedTextArtifact {
37 /* Image dimensions */
38 private static final int TEST_IMAGE_WIDTH = 200;
39 private static final int TEST_IMAGE_HEIGHT = 100;
40
41 /*
42 * The artifacts appear when text is drawn ontop of translucent
43 * background. In other words, a background with alpha channel.
44 * Hence we test the algorithm for image types that contain either
45 * straight alpha channel or pre-multiplied alpha channel. There
46 * are few other types as well that contain alpha channel. However,
47 * it would suffice to test on the most common formats TYPE_INT_ARGB
48 * and TYPE_INT_ARGB_PRE.
49 */
50 private static final int[] TYPES = {BufferedImage.TYPE_INT_ARGB,
51 BufferedImage.TYPE_INT_ARGB_PRE};
52
53 public static void main(String[] args) throws IOException {
54 /* Iterate over different image types */
55 for (int type : TYPES) {
56 BufferedImage testImg = getBufferedImage(type);
57
58 /* Draw anti-aliased string and check for artifacts */
59 drawAntialiasedString(testImg);
60 checkArtifact(testImg);
61 }
62 }
63
64 private static BufferedImage getBufferedImage(int imageType) {
65 /* Create a Graphics2D object from the given image type */
66 BufferedImage image = new BufferedImage(TEST_IMAGE_WIDTH,
67 TEST_IMAGE_HEIGHT,
68 imageType);
69 return image;
70 }
71
72 private static void drawAntialiasedString(BufferedImage image) {
73 /* Create Graphics2D object */
74 Graphics2D graphics = (Graphics2D) image.getGraphics();
75
76 /* Fill the image with translucent color */
77 graphics.setColor(new Color(127, 127, 127, 127));
78 graphics.fillRect(0, 0, TEST_IMAGE_WIDTH, TEST_IMAGE_HEIGHT);
79
80 /* Drawstring with Antialiasing hint */
81 graphics.setRenderingHint(RenderingHints.KEY_TEXT_ANTIALIASING,
82 RenderingHints.VALUE_TEXT_ANTIALIAS_ON);
83 Font font = new Font("Verdana" , Font.PLAIN, 60);
84 graphics.setFont(font);
85 graphics.setColor(new Color(255, 0, 0));
86 graphics.drawString("Save", 30, 65);
87 graphics.dispose();
88 }
89
90 private static void checkArtifact(BufferedImage image) throws IOException {
91 int componentMask = 0xff;
92 int colorThreshold = 200;
93 int rowIndex = 0;
94 int colIndex = 0;
95
96 /* Loop through every pixel to check for possible artifact */
97 for (rowIndex = 0; rowIndex < image.getHeight(); rowIndex++) {
98 for (colIndex = 0; colIndex < image.getWidth(); colIndex++) {
99 /*
100 * API: getRGB(x,y) returns color in INT_ARGB color space.
101 * Extract individual color components with a simple mask.
102 */
103 int colorValue = image.getRGB(colIndex, rowIndex);
104 int colorComponent1 = colorValue & componentMask;
105 int colorComponent2 = (colorValue>>8) & componentMask;
106 int colorComponent3 = (colorValue>>16) & componentMask;
107
108 /*
109 * Artifacts are predominantly a subjective decision based on
110 * the quality of the rendered image content. However, in the
111 * current use-case, the artifacts around the edges of the anti
112 * aliased text appear like spots of white pixels without any
113 * relation to the color of foreground text or the background
114 * translucent shape.
115 *
116 * To identify the artifact pixels, each color component from
117 * the testImage is compared with a constant threshold. The
118 * component threshold has been set based on observation from
119 * different experiments on mulitple Java versions.
120 */
121 if (colorComponent1 >= colorThreshold
122 && colorComponent2 >= colorThreshold
123 && colorComponent3 >= colorThreshold) {
124 /* Artifact has been noticed. Report error. */
125 throw new RuntimeException("Test Failed.");
126 }
127 }
128 }
129 }
130 }