[英]Exception while reading image ==java.lang.IllegalArgumentException: image == null
[英]Exception "java.lang.IllegalArgumentException: image == null!" in ImageIO
我正在尝试从字节数组中写入一个png
文件。
我的应用程序抛出以下异常"java.lang.IllegalArgumentException: image == null!" in ImageIO
"java.lang.IllegalArgumentException: image == null!" in ImageIO
我使用随机字节数组测试了我的解决方案,如下面的代码片段所示,但仍然抛出异常。
你能帮我找出为什么它会被抛出吗?
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.IOException;
import java.util.Random;
import javax.imageio.ImageIO;
public class Main {
public static void main(String[] args) throws IOException {
String fn = new String("C:\\Users\\frogwine\\Desktop\\P1.png");
byte [] data = new byte[256];
Random r = new Random();
r.nextBytes(data);
ByteArrayInputStream bis = new ByteArrayInputStream(data);
ByteArrayInputStream input_stream= new ByteArrayInputStream(data);
BufferedImage final_buffered_image = ImageIO.read(input_stream);
ImageIO.write(final_buffered_image , "png", new File(fn) );
}
}
堆栈跟踪:
"C:\Program Files\Java\jdk-13.0.1\bin\java.exe" "-javaagent:C:\Program Files\JetBrains\IntelliJ IDEA Community Edition 2019.3\lib\idea_rt.jar=57315:C:\Program Files\JetBrains\IntelliJ IDEA Community Edition 2019.3\bin" -Dfile.encoding=UTF-8 -classpath C:\Users\frogwine\Documents\deneme\out\production\deneme com.berk.Main
Exception in thread "main" java.lang.IllegalArgumentException: image == null!
at java.desktop/javax.imageio.ImageTypeSpecifier.createFromRenderedImage(ImageTypeSpecifier.java:925)
at java.desktop/javax.imageio.ImageIO.getWriter(ImageIO.java:1608)
at java.desktop/javax.imageio.ImageIO.write(ImageIO.java:1540)
at com.berk.Main.main(Main.java:23)
Process finished with exit code 1
嗯,这并不奇怪。 从ImageIO.read文档:
如果没有注册的 ImageReader 声称能够读取结果流,则返回 null。
将随机字节写入数组不会以任何格式创建有效的图像数据,因为图像格式具有标准结构,该结构至少由标题组成。 因此, ImageIO.read
返回 null。
正如 Leo 还提到仅将随机字节传递给 ImageIO.read 方法,您无法获得随机图像。 您将获得空图像,当您将其传递给 write 方法时,它将抛出此 IllegalArgumentException。
相反,您可以创建具有预定义宽度和高度的空图像并设置 RGB 颜色值以获得如下随机图像。
import javax.imageio.ImageIO;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
public class Main {
public static void main(String[] args) throws IOException {
String fn = new String("C:\\Users\\frogwine\\Desktop\\P1.png");
ImageIO.write(generateRandomImage(300) , "png", new File(fn) );
}
public static BufferedImage generateRandomImage(int numOfPixels) {
final double ASPECT_RATIO = 4.0 / 3.0;
int width = 0;
int height = 0;
byte[] rgbValue = new byte[3];
BufferedImage image = null;
SecureRandom random = null;
try {
random = SecureRandom.getInstance("SHA1PRNG");
width = (int) Math.ceil(Math.sqrt(numOfPixels * ASPECT_RATIO));
height = (int) Math.ceil(numOfPixels / (double) width);
image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
for (int x = 0; x < width; x++) {
for (int y = 0; y < height; y++) {
random.nextBytes(rgbValue);
image.setRGB(x, y,
byteToInt(rgbValue[0]) + (byteToInt(rgbValue[1]) << 8) + (byteToInt(rgbValue[2]) << 16));
}
}
return image;
} catch (NoSuchAlgorithmException nsaEx) {
nsaEx.printStackTrace();
}
return null;
}
public static int byteToInt(int b) {
int i = b;
if (i < 0) {
i = i + 256;
}
return i;
}
声明:本站的技术帖子网页,遵循CC BY-SA 4.0协议,如果您需要转载,请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.