java - 调整大小图像质量下降

Question

我正在使用 Base64 图像，我必须调整它的大小，我现在使用的代码以某种方式完成了这项工作。但是我注意到我正在失去质量并且图像没有我设置的尺寸。我不确定原因是什么以及如何解决。

例如原始图像是这样的:

但在调整大小后图像质量下降很多，最终图像看起来像这样:

这是我正在使用的代码:

import java.awt.*;
import java.io.IOException;

import org.opencv.core.Mat;
import sun.misc.BASE64Encoder;
import sun.misc.BASE64Decoder;

import javax.imageio.ImageIO;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.awt.image.BufferedImage;


public class Base64ImageUtil {
    private static final String JPG = "data:image/jpeg;base64,/9j/4AAQSkZJRgABAQAAAQABAAD/2wCEAAkGBxMTEhMTExIVFhUXFxUXFxUYFRUVFRUSFRIXFhUVFRUYHSggGBolGxUVITEhJSkrLi4uFx8zODMtNygtLisBCgoKDg0OGxAQGi0lHyUvLS0tLS0tLS0tLS0tLS0tLS0tLS0tLS0tLS0tLS0tLS0tLS0tLS0rNy0tLS0tLS0rK//AABEIAKgBLAMBIgACEQEDEQH/xAAcAAACAgMBAQAAAAAAAAAAAAAEBQIDAAEGBwj/xAA9EAABAwMCAwYDBQgCAQUAAAABAAIRAwQhEjEFQVEGImFxgZETMrEjUpKhwQcUQmJy0eHwM7LxFSRTc4L/xAAZAQADAQEBAAAAAAAAAAAAAAABAgMEAAX/xAAkEQACAgICAQUBAQEAAAAAAAAAAQIRAyESMUETIjJCUQSRFP/aAAwDAQACEQMRAD8A8YMLQWHdSLOhXHGmhFBo6D2Q9LdF0cmFxxdeWheGPY2WkQSAMHmiadoIGB7DdD8Ov3UHxuwnI5J7emmAXg/NsrRSITkzneJ0QMgCPABHdkqLXVstBgE5AjCjdadDk67C8OD6T6nMEj8glcfcPF+0Y9q+G0zTpXDWN0nuvhoADuRIC5b92HzNAjyC6+4uwLevTOxaYHiOfmuOsHjS4ErppWCDbQytNBiGt9gnVG1YR/xs/C3+yR8JogCV0Fnlqyy0x6A+M2rPhmGN5/wj+yR8G06iC1vq0FdJxIzTcFy9iYf6oxbsK6Oi+Az7jPwN/soGgz7jPwhSa5bJWgQpdRZ9xn4QtfBZ9xn4QrSFqEAlX7u37jPwhbFuz7jfwhWtKi5y44gbVn3G/hCw2zPuN/CFY1yk5cEHNBv3GfhCvpNY+m6n8Nk9dI+qgHNmC9o89vWNkNQv203yTg8x+qMWrBJOgqxsaNLUHNaT4gFILzQXGGt9AEZXug97nAyOSW1MHZPJokk3sstKDTUYIGSOQ6r6L7O8LofBZNvROBk0mE7DnC+bqdWHB3Qyvf8AsxdOrWbXMMHSD6wMLg2zXbmyoCkGNoUWlx5U2Ax6BcozhlFtMAUqf4G/2Vl9xCs+s5tfZm3ioniDIgE7KkVSJzkA/uFOD9mz8Df7JDxK2Y0f8bQ7kdIghdJ8QekZXL8evRmBscJ1ROxbcUmkiGt8e6FMWjXCNLZ8glpuySmXA7kGoAeqTnHorUkJbugAY0gR+ay0twTmI8ldxWkW1nt/mJ91RVr6WwNz9Fnapmq9F1Sk3oPZTZSEbD2VFs8kZRzBhIxWc2VtYsRGLaO6JpOhyHpq1pyEUcMatAHkpMp4jkrKQlqicKyISBLsEArr/wBm9b7N7PEnzwFyXEflHmnfYm50Qf5v0Q+wfqVcau8vZEGT7SkpwE07R3EXNQRzx5HKWVSDhSlJ2UjFKI34Ke4cp7Z1owuT4PX0mOSe06uVnmtjsOvvlPkuTYYqLpalWRC5y5ZFQLosVD+mcBXMVNJ3dCnTctKehKLHBVOUyVqFwTTVF6mUFcXg1BjZJ5xyHieSFhJvug3cgYnPPwHUoG8v67ubRjI+WQOZM4RVxYa92HGdXLbLesICpbVMuJjkB1CZY5NA9RJ9i+pcvJ+aB4bD+6qqVDyeSPGRPoUZVtTvEef9kJUt3eaDg0FTTNsrA/M31GD/AGKup1SM/M3r0PRw5eaBcOhVltWIJxPXxbzBHNL0MM2UWvkB0H7vn0K9n/ZJLLbQ7+EuHoF4caUd5hIIy3+k7+YHRd92E7WCnRqMPzhpcAObjEFvgU8XsSSHPa+/1XD2UwJHzHkASuOouf8AHIgxIE8jKM4JxP41xcGr/GYg9Gjb6pvQ4eILh1wqK29MlOo9oMrWuimCcyP0XB8YZM+a7riV034BkxAx7Lz66ug4QD6KrIQ7ArWhseY5I+yZ9oOUZKrpd3KoFUgkyo8Etl+VgvFLkmrUcObilpMq6rsVSpN7NHSQTaPgprPRJKZyum4fQY5gP6pWA5QKYCgrWjCITYV7W7IdqNY3CKAMKJgT1VrXAqlg7ixmVaJGQLxmBEcwmVkNDWAdJ90n4r8w8kx4eZpNI32QXyG+pLtDTmqCebQfySt1PoU2rPmo2RIaBI8FVxD4bnzSBAPLxUpq5Fo/EXW5LXZTugJKVuoF3ojLVphJKDFbQ1YMwEq4tTh4TIOLRKWcSqa4KikchhZVJYESCgeG/LH+7I4LVHoV9lzSsBUHqupW0iVxzLzSfUfTo0xNSq4Mb0BPM+AGfRdnb9mKNABo75B77zBLnc/SUk/Z60urVblwgUaehn/2VTv6Bv5rrHuLWEESCeWSCTunxrySyS1Quv7NpkCPJIOIUWiJ2aMeJ6p29tV1WBhoH/xiZSjiloQ3vE7kDlK0JmaSOcr98yAqHsY0HAkoqvRdMAaR+ao/dYyQSmYYsT3NoXEkINx08gHCIPSP7rpH05EGGhJeJ2+kzuFDJDVmiE/BQKhIDTgiS1w6uzB6hW2NVxeHM7tVpwNg482odxgMMcvoUTWsnOqF4Ia3DtR3GAcBQouFXLiz7RoI1faAHcE/M0+RkLs+DcT+JSYRz/0rj/3jU0N+YAky4ZJdvgJlwa+az7F2NWWxAjwXYppTo7+nG5Y1L8GHaK0pOGKhBnIBwuU0sacfmurr0yBDKOvq4zuuevbd8kuY0eSvLlZmg48Shz522VVZ8ArHGELXqckrddjxWweqcKpW1jgKoKJol2SaUytqrtOEtCvp1SAuFBiFYdlFrZVgC4JGm1MG7QqbWnzRLGp0hGwljoaAraDxKEefosougqiJsq423vNjomdjRgNCWcUqSWnwTZ1bTSa/+VBfJh+qFnEHkVCRMbIqg4FmRnkUC+oSIPiURQuJYW4kbLO3bs0rWjKjyfNUtrwVlW4a4TsQhDUlVTIyWzpm1NVMH/YSy/qDYK/gtSWlp9ERdcPMSRHSRyUJKmNEr4U7BRo3Srh9QB0JrSOVSPQH2Xoctl7QVc94S/ilxoIcNwEyAz0zhFzRtqB1EAvId6NEDHuqXcZpVD9lOJM8iBuuM4jxf4z9FNshmluuDHQTybnmehR/ZGoKhLQBONQ5ZkSPNaE4tmSUZJHRjiukudGAJ88QlPEuP0WNdqYS4Dedic4wnF9bMY12o4gAY6ZXnvHTJMeZ80dAX4Qr9oJPdpiepURxGodwCOiRaoBdpLpwAOTuR2Tc8EqNb8TWAQ3VpOCR4Dmpf9FOmaPQ/B3w6g2q1xiCBsULx+3lgxCt7NXY1jVAkQehlW9rKeJGytytE6pnGaZafDV/vujy1xZvjHePIR9UvnB8nf7+aa3TWtp0nPeIdnQNz4x0WTyakQsWFx0s9yenildzVcTqnyPTomttdt+K2BDQ9ojn0P1Sq+pOY5zTycR5ZS0M5Nof8K7SVXN+HGQN+qC4jc1TlxS7hT4qtXT39qHs8QrxuS7Mk0oy6OYNQlZRp6nADmtVGQYRFhh3oVNmiC2gS7ZGCqAiLwzt4qhIh5dmBWNKrCm1EBuh1U2NJ9VClsAjrZoRSsDdEmNiFcQsqM2WPcqVSJWacVBV1H5WMcuTA0Q4hs1H3xinSb4ZQHEDhiOqan6BEmAISvyPFdA5+WTvyVQBGUfxS0NNrQ75uiE0YUF0aZbZU5oIwhmhW1GwVCluqIjI6HsVS1XDARIJz7L0jtlY0xbfQrguwj/t2j+b9F6F21bqoAD8krWwJnj1MkOTSkSh2UftAPFOjbQFyl4CwAyUv4q3qnNOiZ2SjiTCSQqJNi2h9w6wo1KGmvVNIVmtc7cSA0aSBEGCD7ro+zYthVY227zadIh9Q4LjqbpB680XwezoXVpQ1sDtLGYyIGmIPqEc1jKLmUmNa3EwMQ0EDb1TRwrlyJyy6qgDtdcaQIJk+XI9F59fuLpjnhdN2tqHXuOu+wk7rkbmvpI81dqkSXZPh1CozLWNceh/QIqv8eo7VVx4YAgcgByWUr1oyh7niLn4U/Sh2U9ST0MOGU9VRo8fJF9rHHTHohuz9cMeHOPUepWu1FaQPEqiFo5Se76H/sq7kd71HoOim7Yen/ZRuPn9ffKyGktoCQ885BHmDKL7SNmrqbMOax2fvFolCWZztuSI9EdxdpdToVAQe4Wnza7H5IBArG2748MldY0930XP8G69U9Gy041SMmZ3I566t++VW+nDgn1O01GUurUNTn8oCE1SbKYfdNJCOq0jdQUnMMxk+QJ+i0WEbgjzBCgXZorAVhWlxwbb0YE9UQwLKB7oVtNoKqkSkyZ2CFe/KKuRAAnJQIpkFCb3R0Y+SLzlbpqsnKvt90qOaNcQbhi6Lsxb941amGsGJ6rmLypqcI2CaX3FiababcCBPikyfiLY9dlfFr01qrncuSm0yzKCpZVrKkBBKtBuyiuVUwZRQZqKpc2CnJtjvsrV012nxXr9Gy+Kxpcf95LxXgTvt2DqQPdeziq6lRwZx+iEgRPKeP0PhXLhtBwjGVyQ1Adparn1tRCK4Vn0SqNseT0PbVzA0zuktzTb3zH/AICFv7ioKsDZGiu34RB3W60tGR32Fdm71zKDdJgtJx/KXEj9VDh17VuLyo4PILW6QfEnmOeQkVPiJpfCB/45h/8AQ4wfbf0Ti2uhZC5qHJLmgEeP8XtlRx5G9PwX/oxxTTh5S/0Ucdp3QrObVJceRGx842QDLY85R3E+JVXnUYaOjn97IwSPJLWVXcjnPXklclYFF0Y4lpgqxhVb6pcBLYKutgnTFYZbNiCSrOK1y9zQdgq2dShn1NTp5CU4gsfsPT6lQr/OR4/UKbo7g8R/v5qus77Rx8f8LM+zSgnho74HV36I+5pONBob/C4zHUk/4QFgDrBiAefkMiU14bdFkxEkOInILoDh+qUYzgdrVz9m7zOPqnz6UNgkA+aQW/FqtU99xAnlhMalmHAEEq8XJrRnmop7LX3zWCASeqTXN23vaRB890/tqIY2AAXHmlFfh7dYA+ae85TzPiqbL/zRcncVVBtv2ooUrduim34sQe6MR1XKX9++q7U8+gwFZxegGv7ux5eSBU412NJVo2FpxWwFhCIodYVZEFG02JRbPhwKf24DshWg7JS0BcQfkDoEK1ytuzLyVUwYU5bZSPRovJWE4hEUaambaZXcReSQvKsqbAqFVsGOiIfkYS0PZlu7ZTrYVVDCsq5RSOb0E22yruaSsoDCuOQiuyTA7WoWuDhuCD7L0LhnGqlWkAQMYXnr+fqu17C0y7cSNMgJpBiLO1LwDGCUP2Wd33Fx5YCL7d0wKjYwYJI9cfqkFhULSXBGPYJdD2vWa6o7wSh5lx6T+qs4TSNR7iTzR9S0ACeuWyV8dCbi7O6n3AL0VWUXOALqZ0PHI6R9mSD1b9ClXFx9nHj/AL9Vb2RuAz94JEhoa49YbMws0p+k3I2Ri8sVEO4vxyKkGg06TjuA45ZSOpxBz3ZEeEQu1v7ygGNIAOsBwdjLSMLkr25YTjHstTj5MsZsFqjUt0zC2XhUVLhAJdVqmIV/D4Bg8xHkgWOO6LonIK6wUKnjLB4x7FU1D3neZ+pV9c5H9Tv+xVES4+ZUWXXQxsRhvTWc/wD4VtiYLRg7A+5aRKDtzhw5BrjtzIA3Vk6gC2SXbD+f/wAhKMW8PAbVdTP3iAfEGAugtvibBjvZZbU2ik2uKILjEmCTqGCR6o11aqXNHIiekHopPM4t0aYfzRnFNltpTLJ1ZeRhu8IfibW0qZMDUcTzRX7/AE2NOwMbk81xXEuKvqOIB7sx5qS5TlbLSccUeKArp+oz5/VUQm3Ga7XlukAANAEDpzSyFoTMbVs0wLCsYMqw05XNhjG0QphFWVUsMj2QoEImgRBHNOmyJa8EyVU0q2zfIKk6lhN2C9hFoj+HEaih7CkCAra9EtEhWSISdsXcUpfaxsDzVVFuYWqxLniVNghQ8l18TH0YJWmnCJHenqhMynqhL8BNB/JEsGEviMlMKRwpz1sPgDuWxK9X7F8H/wDbtcdywHHiJC8ru8r1nsndv/dWgcmgecBO9o6Ojk+3fDSS17ZOPXfK5G2JgiF6VxvNN2rlPouA+OM4RUfIrl4CeFQzfEpk57TzCRurSqnvIzqTcuK0LwUnst4w+YGI7/n0/RQ7NHvV2/eo1PcAQq6hmN/lPvnZV9nqumo88tD59WuWTLuLNmKotIVMuXaQ2cch08kZw2h8QOyQWxjwPNLyEw4G4iq0fe7v6hWj2RktOiFam4GCVjE54ja7lKIhPJUycXZYH8lbQJQ8q9jXAtkRJA6nJjYbrrSDxbBD9HfVxVNL5z5/qj7+z+HgO1DUMlhYcEjYoF7NLj05Kfe0Upp0yyjOmp/SfzKlZ1Yb4tc1w8gcqLCQ2p5fRwP6Kuk6CDyP05hcEf0uLPpUnBo7oft4Ek/qtf8ArlQmQBt5oOzhzarCJJZLTAnUzO89AqJApiAQ6cnkpOMW+i0ZyS7Kblzqhc9x9P8ACGCtrNjnvutBqd1FCJOTGF1THwaZ5oCE1uWfYU/KUtDVCDNLiQYzMq7UAtnAUG0i7KZ7Co8eiy6ti3y5FDvGJTx7cQRgpTe0YOkZWzJCtnnQleiPDZL4HNPG0AcJdwizIlxEEJxbQPFHHHRPI9mralpwrrunLVN7VVUJmDsqkrEdGmdeeRRDxkqVIwXCPmdAKwtyVmXk1S0kRp4yh7od6RzRQGFlWlIBhVatEk9i+pKNs6khU1wrbPZRmtDxK7qplerdgrgOtg3ovIaru8V2/wCzniuguYduS6PQ3Qy7aXehrhzK87aSXea6ztvVNSsGjbn7lc5WoaSOqacqFgk7LG2jiQBzR1bs/U0TKN4WydJTq/f9m4jk0/RUUbRKeRxdI4SqCHEbd0n00pe2tAfG+lon1EpvxN32jyPuaR5Bun9Ehn5h4fSFBo1JlblbaVgx7XEEgEEgGCQDkA8jCqOy0VwDqv3h2sh7TodlpBBIYcjOyVXj2lxLW6fCZTPhDtdu0ndpLT6EkfkQlt5a5lpMJpxk6aZGLSbTBQZyrKQhwJM5HjzU6VBQuDEGNuW49R0R46H5bCL6oCwbDvbRGxPiVu4tw5hPOW/mYQt1Xc8AuABJkQA0QT0CJqP7pA5rsVVQ2R7sEs3RUh3PBHnhU0u64sd1g+HQoy9LXHG6les+NoeB33Q08gXDHvEe6Eo0FOyFsTTeHD+E5/pOFlSgWvIfgbjxactR1S0+E2g81mOquJ+zE/KMiXeO0KnjBIawbsglj/D7h8ip6CxZUAnBwrmsCHp7o5jRGyTI6NOCNh1z/wALfIeiWsR9Z/2X5IBoUomnIto0RJ8Fp1XotPM45Ks1QMBORcqOgpv6rGUYqsf0IVAejLZ4OF6bV6PLuth/F6Q3GCUDRqBsSt3NRwOdkHckFuCslyxyNLUMq0N6rpQd3VAHildG7cMFTqVQYJOOir6qM6wOyTany/1SpVHZlVNqA5ClSypJlJ+C0KTT3COa1TCsLQrraIPsWV1ZbOwqrgqdoptXoojK1D80ZaXXwSCFQ9+VG5pE97kuSo7sc2vEWveXOQnGHhzpCWMKtIJCSTbHSSOhsLgCm1FXV19i8+Ee+ErtKzfhgc0TXyxreRIB8t1Vv2kZU30c9eGHOM/wj3Pe+qUzn3Te+Or4h6uAHp/j6pSfm9VE0Loi7ZaAwpOP1W+g9VwR9wJuiWkyHjV5Ef4UqrclDcNpv+LTqEdzIB5HEGAmt7Qggq8VcTNP5A7KGEq4hTgev6LpbajLSY5JDxGiSWDqTjnjcrpLR0H7ga3AEyeQ5NP/AGK1VfHqiDDQ/JmBsAefOf0QtCkSZKkr5Oi7dxtk7W2Lk0oWr3lrKVIv72agDtJqA4EnGBiQibCiRpDWai4xJHdZTB7zjOCeULuzxJhq29NghoY9wEbuGiCI6CQVHNlcWopD44X7mcjwSqGOfSq02u72Q8AierTyPiEdxrsh8dpfau8fgu2nnod6Kvj7B+9vxGxjlkckRZ1XDmQPMhbMcVPGmzNklxm0jz2vavpP0VGOY4fwuBB9OoV7HeK9Xe2jcs+HcaXDlrAcRyw/5m+hXO8X/Zy9oL7Z+tvJpIPoH8vVRy4fw1YM6XZyLnfZlAkyjLijUph1N9NzXDcOEe3XzCXHxWdRrTNU8qdNEnv6KsLYCkHJ+iL2N9Q6j3CnTeAfmHuFixbFIxUMWVw5sEt9wlFeGncGfELFiTJtD4/bLRupSa5uCPcIN1ODEj3WLFmXZpk9F9qBG4x4qyg8dR7hbWJ0QnsKpub94e4VtRzY3HuFixVi9EZITXREnI91pjxG6xYlY6ROlEjPPqnvEhTFEQ5s+Y6LFiMWBoQ0njaQnIYwUtx7hYsXQ8hl4F1GuAIkb9UdVuxpBkYB5jciFixK3o6vcKnvBpuyN+qAdv7rSxKVLqVHVqgjutLiSQPQdVlhSa5wL/kG45u8AtrFwDo7KuKlVpOlrGiGiRATa8tWluHtOfvD+6xYtMPiZsiuQdbUGNaQXs2+83c+q5vjrKNGrrbUD3lpaGYLWbd4kfTxWli6T0GC2J6Fk6qZkQeZIEpsOHCm3U4ggcg4aj4DxWLEkXqwvbC+E2tS+e0mrToW9Jw0jUA7G0NnPifyTP4YpVqYD2wyu4TrB7rg2TM7GVixY0qmbG7gXcTDDcVHB7DhudQ+6gLi4HJ7fxBYsW7C6gkY8sE5tg4vIPzj3Cc8H7UmiR3wWncSIWLE7dixR0/Erayv6OX0w4jB1Ma9h8J+i8a43wl9tVNJ7mujLXtIIe3kR0ONltYs+RGmDYvc5aW1ikUP/9k=";

    /**
     * Decode string to image
     *
     * @param imageString The string to decode
     * @return decoded image
     */
    public static BufferedImage decodeToImage(String imageString) throws IOException {
        BufferedImage image = null;
        byte[] imageByte;
        BASE64Decoder decoder = new BASE64Decoder();
        imageByte = decoder.decodeBuffer(imageString);
        ByteArrayInputStream bis = new ByteArrayInputStream(imageByte);
        image = ImageIO.read(bis);
        bis.close();
        return image;
    }

    /**
     * Encode image to string
     *
     * @param imageFile The image to encode
     * @param type      jpeg, bmp, gif, png
     * @return encoded string
     */
    public static String encodeToString(File imageFile, String type) throws IOException {
        String imageString = null;
        ByteArrayOutputStream bos = new ByteArrayOutputStream();

        BufferedImage image = ImageIO.read(imageFile);
        ImageIO.write(image, type, bos);
        byte[] imageBytes = bos.toByteArray();

        BASE64Encoder encoder = new BASE64Encoder();
        imageString = encoder.encode(imageBytes);

        bos.close();
        return imageString;
    }

    /**
     * To make base64 string decoded properly, We need to remove the base64 header from a base64 string.
     *
     * @param base64 The Base64 string of an image.
     * @return Base64 string without header.
     */
    public static String removeBase64Header(String base64) {
        if (base64 == null) return null;
        return base64.trim().replaceFirst("data[:]image[/]([a-z])+;base64,", "");
    }

    /**
     * Get the image type.
     *
     * @param base64 The base64 string of an image.
     * @return jpg, png, gif
     */
    public static String getImageType(String base64) {
        String[] header = base64.split("[;]");
        if (header == null || header.length == 0) return null;
        return header[0].split("[/]")[1];
    }

    public static BufferedImage resize(BufferedImage img, int newW, int newH) {
        Image tmp = img.getScaledInstance(newW, newH, Image.SCALE_REPLICATE);
        BufferedImage dimg = new BufferedImage(newW, newH, BufferedImage.TYPE_INT_ARGB);

        Graphics2D g2d = dimg.createGraphics();
        g2d.drawImage(tmp, 0, 0, null);
        g2d.dispose();

        return dimg;
    }

    public static void main(String args[]) throws IOException {
        String base64 = JPG;
        // convert base64 string to image
        String imageString = removeBase64Header(base64);
        String imageType = getImageType(base64);
        BufferedImage image = decodeToImage(imageString);
        File imageFile = File.createTempFile("image", "." + imageType);
        image = resize(image, 600, 800);
        ImageIO.write(image, imageType, imageFile);
        // convert image to base64 string
        String newImageString = encodeToString(imageFile, imageType);
        System.out.println("Image Type -> " + imageType);
        System.out.println(newImageString);
        System.out.println();
        System.out.println();
    }

    public static BufferedImage mat2Img(Mat in)
    {
        BufferedImage out;
        byte[] data = new byte[320 * 240 * (int)in.elemSize()];
        int type;
        in.get(0, 0, data);

        if(in.channels() == 1)
            type = BufferedImage.TYPE_BYTE_GRAY;
        else
            type = BufferedImage.TYPE_3BYTE_BGR;

        out = new BufferedImage(320, 240, type);

        out.getRaster().setDataElements(0, 0, 320, 240, data);
        return out;
    }

}

Answer 1

我做了这个小改动:

BufferedImage dimg = new BufferedImage(newW, newH, BufferedImage.TYPE_USHORT_555_RGB);

然后使用 TYPE_USHORT_555_RGB 它对我有用。