在 Java 中将文件编码为 Base64
Encoding a file to Base64 in Java
Imgur API 允许您发送图像的 Base64 以上传该图像。
我已经测试过，当我发送一个如下所示的 Base64 时，它是有效的：
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
这个很长，由网站生成http://www.base64-image.de/step-1.php
但是，我的应用程序代码生成的 Base64 看起来像这样
_9j_4AAQSkZJRgABAQEASABIAAD_2wBDAAYEBQ
它更短，我不知道为什么。有人可以向我解释如何获得长版吗？太感谢了。下面是我用来获取简短版本的代码。我显然花了很长时间谷歌搜索来解决这个问题，但似乎没有人对这么长的东西感兴趣。
String file1 = "C:\Users\J\Desktop\test5.jpg";
System.out.println("HERE");
FileInputStream imageInFile = new FileInputStream(file1);
byte imageData[] = new byte[(int) file1.length()];
imageInFile.read(imageData);
byte[] encodedBytes = Base64.encodeBase64(imageData);
System.out.println("encodedBytes " + new String(encodedBytes));
String convertedImageData = Base64.encodeBase64URLSafeString(imageData);
System.out.println(convertedImageData);
下面是这两个的输出：
HERE
encodedBytes /9j/4AAQSkZJRgABAQEASABIAAD/2wBDAAYEBQ==
_9j_4AAQSkZJRgABAQEASABIAAD_2wBDAAYEBQ
感谢阅读。我试过很多不同的东西，现在来这里问。
imageInFile.read(imageData);
不会将整个文件读入数组。
它读取一些与其内部缓冲区匹配的字节长度，returns作为实际读取的数字的结果。
您需要循环重复该过程，直到不再读取 returns 数据。
检查javadoc。
试试这些方法：
public static String imgToBase64String(final RenderedImage img, final String formatName) {
final ByteArrayOutputStream os = new ByteArrayOutputStream();
try {
ImageIO.write(img, formatName, Base64.getEncoder().wrap(os));
return os.toString(StandardCharsets.ISO_8859_1.name());
} catch (final IOException ioe) {
throw new UncheckedIOException(ioe);
}
}
public static BufferedImage base64StringToImg(final String base64String) {
try {
return ImageIO.read(new ByteArrayInputStream(Base64.getDecoder().decode(base64String)));
} catch (final IOException ioe) {
throw new UncheckedIOException(ioe);
}
}
取自：Java BufferedImage to PNG format Base64 String
岁月流逝...
如今，我认为可以在这里找到解决方案：https://www.geeksforgeeks.org/url-encoding-decoding-using-base64-in-java/
所以这对我有用：
Base64.getUrlEncoder().encodeToString(bytes);
要将 byte[] bytes（完全）填充为另一个主题...
我测试了在发送电子邮件时添加 html 内联图像...
<img src="data:image/jpeg;base64,_9j_4AAQSkZ...
Imgur API 允许您发送图像的 Base64 以上传该图像。
我已经测试过，当我发送一个如下所示的 Base64 时，它是有效的：
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XVTmZ+iO0dM8Chs21GVx63b/AHWZpUU2uceQU7M/VTEDnZNlhAO9ZwOQlGW390MWWVrPavP2W9aFWY76PKG2bUI5PXleowx+YSsmL7QskgLFhzcVElvu1XB7f//EACcQAQACAgEDBAMBAAMAAAAAAAEAESExQRBRYXGBkbEgocHR4fDx/9oACAEBAAE/Iduow9YTmcdDJgKh4uU/i3MyuoMdvUh1OgigVI8k8ez7r/0hnXtFjK4dxR0qVE6PQ8/hfUjL4H8c/AmNv0HL2g6M2vB/3zCCHmP/AAeSYbtet7h/jEA0IJKiSo9TuV1Iw6EccTs+XiKvcFfPaNXCYN0cnPGR9ZWaXh6p3P6S3qLv3iEosHWxyuIq1GPqfp0qPQYj+bydvlwBB+XXtmsfUMW9ncjKi42Qroav3AinePJGG0EVd+UEaVh7RlMAAMAS6l3FF6PP5Ed4EP0tcvQIXHIgXlitCkeWZgDApPJ7yvd9EMuMFselUSuQ7eSWNByP1LUJEwk2lzToMda6V0CMzAKexqDbi3dygG8Qnx4irC6JVy4q/NDskZeolqxtIN1LtO8s9cBFXLvlcUzENQEwhF6aznrUqGZa9Kx3nb8DDFojiOqUOYJfIEfGYD0p6RxbZY+YxlUFgs1AaHaopIW8hD3F8Shi9HppOepNrHftB4KvDxeEqrZ0tUVdHY+4nL/6B3j8WlItRBqqvEOCinSChVaqWcEa45382TdjCPRY/Ai2WRBV32SjZb0jVTRCmTsWCXTYZQHjfnzNaywWPjIEvrA4unLNWl85PMz+2v7Lo9DoR6Cc9SPjpuJ7mFuwSyhnUw57J/R2mO1vK0oUdVmBIAthtw7SzbGxu4SHmrt4jWEJPZM+E2228r22goDsV+JTn8K9AF8YsnxUC+TcjmvY5jcassMUAoNuI2z4YSs18WHHFzT7Smh481H++DFVXeWgA+Ygha0EVf6mDF9p5TKXCUj1ZeXuUzfJuNh/3xAxqywYf937RaV9TJvla8W8S2AByhOM4avTZXvK0W5L457VKJ7hbfOIJyA5xKxY+LWVEGYGh85WwqtVZxOY4MS8wYgjvpcGbvalExKI/oL/ANmPWFtlZDx5m0DKy/cv+sq3LJdWuv3U2NLlFy77Q0xyZThAgQ8HkWRcE0qn5NH4mVw0aPuRl6PJkrmZacTLcMy6htqXMJcuEMM6st7Q5bdHcpuNstUHIRt5mWtr4ZmvjF3llKgWiGjvOn6gkCg3hX/EFsCA8xeZrybPJ2h2MKwYV7GLF6HhDWpQRuM2qwH3leQENLd757RW20luKO8El1WZ0xTsqX8zPIn7DUuOPCyTaveEN1t3o3FUCpWyGxdNlPaFslzwYrXRXMuMlLYfUlATdge8aJx0McdorW02LeZWPYCaipaFtLxNlnxFp/H3D6CJx3hG++N5gdBiZgDMslRNyoWBKuM5RjeVaApeh5Yi1Lb4/wBSli+Lu8EQz+DtGKzU5G8SV58Q+HGtoK/2Z+8Yq5g6ncldoCtRxGUeirH8mt1HY+sTMZcdEWafr6THqDuHiEuco7jVaHkEeUTR27w6HF31ehLYR69IAWRITh9+mpzBCeUjnJLMKvmHKUuK6QqOWXwyrhVXoQW0oKdu366GIsQaipiaW2Bkx0H3RY5l8sZmUUeC43XjqSqpciicg2A/TcVKjWTmP0F9ujy5KP7Kp1gPYhLgYQKalm40Yj+qWVR4JQLnxmN86eAisQWNw9gnjzKH2YlPxEFPapRecXk1HPbrc+puipUzh9xp/kxMxZxxCwzr94yulycCWo4KPwwudx2yLY2sbz5gvQax+JYyNUco4MQrP94g+EN1fbcshrKNv1KzSXM1FdFyFO7MLmXk4Bi+TPIhmkr3OZa+8piqnnxXM0V93aJk+ADZLii9m7B7bhfKTmxDJR2MQurvxfGJj1wu6zwE7EEFupiDT3Etzbc7cQFYhfdYcvWFmA3HNjXJAOTCCTs1uEgbSwOd8Q2GteL39Qc6OaZ8jL8ygTRwv/KKxuTklXq1ZjwH9imN5rHzPCwmYoGPig/DmMhUat7QW7VcQ/lDdR/sc3ra0ZgUHkwiBR3lx5esDbh32mez8Sns/EKC/YI1gL8TuJ4zBOO8VoR2zV+mPDxeT/Y1Q1dqoiwQlPN+5n5jtLaat8oIyctRngww2ka9I+T4jZ0yns/Ep7PxC04d9p//2gAMAwEAAgADAAAAEHFPQc6ZbIw/crMYmGT4O7zlCwthnch91AzB56vC3beuga3fk8XEe27QmZ37MgnELGj6b84Oqg8brPkMjMT47LLSc4PjMxgrioJcI8O1YoOb36zLZ7iejp+n+gMpFebIupMFsXHXvvfn/IIgP//EACcRAQACAQIEBgMBAAAAAAAAAAEAESExQRBRYbFxgZGhwfDR4fEg/9oACAEDAQE/EA4LIFkVYQ07Wp8+HWXKuBjaQSmBmoOEc1MCpX2luBd7Qr2Y+QR1TXa7HfvLYLKX5c47jx1QohPD4VGnPxLgOPp5ENr086xzrMEzdeutle2+NtZW1/gDDHLq7/EEczu0PcqLtJo8vSHilcuV7wFStKPQx+4rY6SyVKiOjFU9/mIAreTh8Se6EK9GrimsPseL9ZZBctMXgWgcKiOWryrY01yv5YFssFYwctI0vQ++cIO/T75QbDF9fKOAVvrrAxGWxmSAcA0vSv3KtUbHTJcqGmolRmis6bLXREHeWMZz3SDqYXLiPnwLCdUEXKI3FM2w0TpBrWGmNko89MeMoAVV9/rBPIRLG4iaLeEZQufL+9YBttQ5wqvS/jkW9IkK9TTXgc4gg2jHMYLpgyXls35Mq5qxJQwZOf38wpZwd8vavU4LmW+seocJjiTN7BBmMr0gWiVlJmM7wp3198xp3nPwawR9cOcRRiYmryg3dnrOQ2eGZYCqOi/uOZn98I5qE1NbG2ETgAgFzAeIoIbaQDoiaiFIGk2kTHD/xAAlEQEAAgIBAgYDAQAAAAAAAAABABEhMUFRgRBhcZGxwaHw8dH/2gAIAQIBAT8QfBUibh1SGBlaePM9Tk3AC0xHSXt+Bq/EQExXHaNJ1X+QcKKMNpeN2fRFLUjg4p6Vx8S6pjWevl++0oPBcuyaRpVh6Rz6RtjDGIVoI9/fMoZ2dBzXYmpEwdG8/wB7TFAb8SWTihu5rHvGpceaY7QAe4moviHhYbZrAz4FrwO+a8elRymPTU2AQ7MTkchn1iOtolFGrfqClO5WMrMQdBrzva71j+EKt92/eDrY5/ekCOO41yoc8d481AdCGMplEIWjW9dzkg5vn2jPUjNUK3jdef1HhrHwMsh0YrDLzGBWoL0I3YwC27hsDz5rPPbefSWZrcFHDBu+sueIJPiez+/8jhUKrW/xClbydfX3jWOIlUUMxvKyiow8OpcOkFmImgszACm/jB8ygwlXFqblTdqGK+n5gVTQPM+/qCsi7ncYqcQ5kcar9P3MtMKKyfnG3/cwQXA/EPiPtBfh3+oRQD6k16RGy2Zih7/NxLUtBLIomkS8yjEwMTIgRaAtkWNXw//EACYQAQACAgICAgIDAQEBAAAAAAEAESExQVFhcYGRobEQwfDR8SD/2gAIAQEAAT8QsLLt5gucv3LQMv3EeX7ltqi9/cLyt+43yfuXeW6lwgCH0C8XxfqZsrKR2/czu37lt8/czysC0uPMTsnzLXt+4CG37jdu/uMvPPcz/wAcxKgQMygwxHeGDNRyKBrE2JBgbABfTOWgHTm5iSgcexgBEBaFLfiOI7NkTFfwYolIZngwWOeYM0zuJjUB4hiG0IOC4svcyLfuC8jFe/d91A5EsH1RPEbcNw281ydUzVXcrqIUCUi5y+z/AJF5rs8128te87jXb65Es/f/AMAPLHG4CmmswUq7YYTQzLD1MHGplEvITZWVZ8i5HBy10zMJTLbs35fOfUTtByrTdrn5i9rxdU+X9QtR5bPE814H9FUaoQ25Fy3SeIFHhzhLpC67YFQM95FoDgdwFxUaWw3cqZnuWt9sGJuBnMCtRpKgRKIQE5X2l+i2JZE1VWsLWEp7eYzcDBQ335i4am4W7fmEB9oCKyEwHct5XMRppH+o+FEeT4W2scVUuVIdycBXBa34wblAMQBQGgD4lOVR4IxrMGjNQKfcS17/ALmmG2VTmG7JuCriioOwwjzQq+4MoRBgO8/E3HKGW34giKVMXRpdGiXoibAQdtr+IfxVEgc7zsGnxBYABEa4uk341D7DVYjtduBx1pgxWWRRYjBdrlhx3HftG1bhW9za+4mY5RIQFS5qBZu/4Cn1+ZepgdmAwSKcGFYXcdLhloqgMCWZOaxEwjWtBN2B1KQcYOUN0C0aa8Mt2zpWvNvdxBSALICHdKHgtWQXAKAWgIoUux/GS9zlXbCev4EAFjZ3E4AAoyL0yU/1OFGj6jOchX6lDAQbcH/ZZQtKUFQiMBWUdGt4gIwF8enHsnxVlo/3mG2lbVJGeU5LF9y9ODEtl8fwNx5e44Xtg5zC7uZEy+j9XYLr51K+5qN2CwlW5x4jtaeyq2wKEL7R+HApu+Q4047jw75WBpqKS05N3mNrU0NLmQuyx/LKrUgo+JqU4FqwJZoxOzWqLk1cXLYq5ia3bM9w4mpme47+X9xC/wCNCJmaLVibHOtQSJ60mgOAOYwRggPB81Gru8JPIxNxRsyVx/1HaIso3eeJgCa7t0WkJjwGr8MO6lAJdAFXFJOiD4ejxEIbAt6B/ZXwSyXbweI9ShEJOK5gU33Ly9sHuVz/AASY89ooVy0XivsiUwtq2VFl/OJS7VGrVJUKYvljZslVlS6d/D8REFJA/wB5qLOo4bIfgFXysoBNVRLhEf8AGyWcioLtn2rVwQtRdh2wQXbsK8ejCRDZNA+f8qMzJt0W7oiWruXwcS8ZlXiBTnmaY9sIZIYFaALVaAj4TjaWpXrAPQvM0DonVB22/wCGZe7dAKa4zxOfVe7gvkbqvPEOqG8g7OM79QuUMwZlLVVWLlOowGxDCsx8g5qCAC42SwwT9RnEuBJn6inR4Y5Gn8onNdP5lI0MNbtnxK6HueUF+CCj7hpPll4hplVRopB5Hs35quYUtf8A/EA5ffJmOGu7gwAWYDVu/CY72Nza7ZQ6TXssKDWCBYuEb5Mph0HZQsb0fjE3uADFa0KSHWvUuVYxAvQ2K2H3ctKIhYTT6SzHmYIHqocyq7p3EbtQSumzBaeuMy2zfoIbWBq3HUq1ZUt2JdpcsQfmYH3Ff2l+Y01EM3Bn1V0PSdPSUkSnqvm7MFNcIs7jmgEaChYYosbdIGog009Q8lKsUV8w2FeKwCipxArLkBFLMgyuqwiRyquYIL5Vez7qHy1cxohXkz9SnD61OeVPkUaR0IBW7zqzyhCjC6a1YyMOFg0VtbHs4ZUUs9Rla44gxeo/ycscn5js4jdhhW7iXWqnKaqqlNsMLxIcurAXHvKgWVQqFKbrzGpr9VVQzirTsFT8Qc5Yql7KMiVV9LMqGT0ZByhS/EquEcLqiegb7IRYhtmE1C4poasT1CVAsinsPZxHsizeVzYynyvmIKADlIAvtguuIiYn8EDyuo34W6XuR4qNGkHBzfgxpy6jaEmEEgMtuKBdEcaUDQPJ+YbUL5alSi8R4pctWKQJTsOMB9xW57qsNtbruDQzlCq5dM5ZeEiC9kbsYuWmFDmXDKcbyRhmZ05lBXLLRoNzK9sUij4lG2nHMCOGYz0z3niGo+Guw0jPwVL/AIULlsAYC6wfKy4HewcADO9yw0ADQB1KrglBV0iA5ah5IaWoo5Y8MqRh/P3S9j3ys5oXvtV/FmI+LKuWoJdFcS70GK6lq2HqKRc6iJaO2F6t/cSNLq8fctaY7oO9zFdM9Fm/ACstRLRp5H7W/MtmNCz4L8vxG70tH0PEdt2yxRVazLEWd1pXhZCv3mXUEmGBC3J9uWXQgaFbWduAPmKF1bCApmAvAhoblowy+IQFaXhgWLwUdpe6dGMhYVaLduJdPKyq5cc3C/Dcyx2f05qAPc7rUJR9w0RCCJCxFTeLtgyenIItK7Cy4FCuHNMvnMbYtSXhRbPgCAEzZSxKWoBCLYYZL7iClxKTEscNlbKt/bKioomZlAleSrypmHMp8JTA8y4S1fxCXAzLGeY8URzVcq4RKM2Zft/DLn6iRVH2IAq3HSD7QcuoBW84IhRdmPEO0n0ksYsoVW5f7ineHgxcZEAazEKeFt4wrbFrTsP+xMdIAJ4qJMilw852PJLCsycDpnmZqrPGYlLXoISmWjugEzqtPcPYBgbAD9RcksbzLnTLTEyiqWLeeVgNOGzG4kDn6S1UNjaR1QFrYRD1xaIroLT9SxbgxO85fA3FNq6dt5BUPZGr8gADqlIvLAIWdP8A5KGYoOB3nb6gNrxph7NPtIlqcw6o7CvwgqHBSi26u09RV4sEG72vZgiDg4g+oDE4P8I/UdlZXha7dShw8hHoYwehvsl+i5uiewmvmFUSso+aIPwQtY1ahzT0dRcAZAxOiaefxHkGkvD2obL4ipoYAawRIZWC0ZghWUdZ+ec3G4iqgd1X7jcgI7AF/cF8USksDw3xHbpPer0MBLalm/WCA6hbYA7cTkMzXndGYGH2Cq+VX9orsSjK+hl+xOkWfV1El53RW+FiYFYGTtHbr8Iv5lbKA7qvAdZ6l7cyJkHkz5ItAw1WK+oOM3aPQvE2qx2rG5P/AARFrIs/MNJsZ4PMJTLxfj5iWTKuzlxrUMSsSChQDS+4FBZHvrbkfBAe8aJ0W1PcL/FjApzhTDUSlmtBi6LY2mV2TNZClYBkxYmmAEF0TTumJZueW/iVBtsi6y0wvggX7oH0A5Y5W8ZEeHUZ8MdznFoK+4/54AlqtlOdxhPWuz8QmQOBphHMf4EL3z8o7lZ4hyV9yLKD3Ig3y1b9zKVI3dER9rUPvDCJ3hBRxYU/ZGQOSVeeKaMBKb7u9cVHty1xh2VsPmUR1S36MRN2+Be0lwDkKOOyo+e4WS+JVGDwi4l0vajtP0scMxX/AHJ+3R0T/9k=
这个很长，由网站生成http://www.base64-image.de/step-1.php
但是，我的应用程序代码生成的 Base64 看起来像这样
_9j_4AAQSkZJRgABAQEASABIAAD_2wBDAAYEBQ
它更短，我不知道为什么。有人可以向我解释如何获得长版吗？太感谢了。下面是我用来获取简短版本的代码。我显然花了很长时间谷歌搜索来解决这个问题，但似乎没有人对这么长的东西感兴趣。
String file1 = "C:\Users\J\Desktop\test5.jpg";
System.out.println("HERE");
FileInputStream imageInFile = new FileInputStream(file1);
byte imageData[] = new byte[(int) file1.length()];
imageInFile.read(imageData);
byte[] encodedBytes = Base64.encodeBase64(imageData);
System.out.println("encodedBytes " + new String(encodedBytes));
String convertedImageData = Base64.encodeBase64URLSafeString(imageData);
System.out.println(convertedImageData);
下面是这两个的输出：
HERE
encodedBytes /9j/4AAQSkZJRgABAQEASABIAAD/2wBDAAYEBQ==
_9j_4AAQSkZJRgABAQEASABIAAD_2wBDAAYEBQ
感谢阅读。我试过很多不同的东西，现在来这里问。
imageInFile.read(imageData);
不会将整个文件读入数组。
它读取一些与其内部缓冲区匹配的字节长度，returns作为实际读取的数字的结果。 您需要循环重复该过程，直到不再读取 returns 数据。 检查javadoc。
试试这些方法：
public static String imgToBase64String(final RenderedImage img, final String formatName) {
final ByteArrayOutputStream os = new ByteArrayOutputStream();
try {
ImageIO.write(img, formatName, Base64.getEncoder().wrap(os));
return os.toString(StandardCharsets.ISO_8859_1.name());
} catch (final IOException ioe) {
throw new UncheckedIOException(ioe);
}
}
public static BufferedImage base64StringToImg(final String base64String) {
try {
return ImageIO.read(new ByteArrayInputStream(Base64.getDecoder().decode(base64String)));
} catch (final IOException ioe) {
throw new UncheckedIOException(ioe);
}
}
取自：Java BufferedImage to PNG format Base64 String
岁月流逝...
如今，我认为可以在这里找到解决方案：https://www.geeksforgeeks.org/url-encoding-decoding-using-base64-in-java/
所以这对我有用：
Base64.getUrlEncoder().encodeToString(bytes);
要将 byte[] bytes（完全）填充为另一个主题...
我测试了在发送电子邮件时添加 html 内联图像...
<img src="data:image/jpeg;base64,_9j_4AAQSkZ...