使用位图文件数据更新字节数组时，出现ArrayIndexOutOfBoundsException错误。
错误：线程“主”中的异常java.lang.ArrayIndexOutOfBoundsException：819 在test.BitmapResizer.main（BitmapResizer.java:95）
这是一个简单的练习程序，用于缩放现有的位图图像。问题可能与我的数学有关，但是我被卡住了
public class BitmapResizer {
public static void main(String[] args) {
File path = new File(File.separator + "test" + File.separator + "bitmap");
File original = new File(path, "original.bmp");
File scaled = new File(path, "scaled.bmp");
int width = 0;
int length = 0;
int pixelSize = 0;
try {
BufferedImage bImg = ImageIO.read(original);
width = bImg.getWidth();
length = bImg.getHeight();
pixelSize = bImg.getColorModel().getPixelSize();
}catch(IOException e) {
e.printStackTrace();
}
Scanner input = new Scanner(System.in);
System.out.print("Enter scale: ");
int scale = input.nextInt();
int scaledLength = length*scale;
int scaledWidth = width*scale;
int bytesPerPixel = pixelSize/8;
int widthBytes = scaledWidth*bytesPerPixel;
int originalSize = (28 + (length*width)*bytesPerPixel);
int scaledSize = (28 + (scaledLength*scaledWidth)*bytesPerPixel);
try(FileOutputStream fos = new FileOutputStream(scaled)){
scaled.delete();
try(FileInputStream oFis = new FileInputStream(original)){
byte[] scaledArray = new byte[scaledSize];
byte[] bArray = Files.readAllBytes(original.toPath());
fos.write(66);
fos.write(77);
fos.write(scaledSize);
fos.write(0);
fos.write(0);
fos.write(0);
fos.write(0);
fos.write(0);
fos.write(0);
fos.write(0);
fos.write(26);
fos.write(0);
fos.write(0);
fos.write(0);
fos.write(12);
fos.write(0);
fos.write(0);
fos.write(0);
fos.write(scaledWidth);
fos.write(0);
fos.write(scaledLength);
fos.write(0);
fos.write(1);
fos.write(0);
fos.write(24);
fos.write(0); //26
//o = original
//s = scaled
int counter = 1;
int s = 27;
for(int o = 27; o < bArray.length-28; o++) {
scaledArray[s] = bArray[o];
scaledArray[s+1] = bArray[o+1];
scaledArray[s+2] = bArray[o+2];
scaledArray[s+3] = bArray[o];
scaledArray[s+4] = bArray[o+1];
scaledArray[s+5] = bArray[o+2];
scaledArray[s+(widthBytes)] = bArray[o];
scaledArray[s+(widthBytes)+1] = bArray[o+1];
scaledArray[s+(widthBytes)+2] = bArray[o+2];
scaledArray[s+(widthBytes)+3] = bArray[o];
scaledArray[s+(widthBytes)+4] = bArray[o+1];
scaledArray[s+(widthBytes)+5] = bArray[o+2];
if(counter == widthBytes-(bytesPerPixel*2)+1) s+=(widthBytes+6); else {s+=bytesPerPixel*2; counter+=bytesPerPixel*2;}
}
fos.write(scaledArray);
fos.write(0);
fos.write(0);
}catch(IOException e) {
e.printStackTrace();
}
}catch(IOException e) {
e.printStackTrace();
System.out.println(e.getMessage());
}
}
}
第85行的循环应从“ bArray”的迭代更新“ scaledArray”。这个想法是通过将原始位图的每个像素映射到另一个像素上的多个像素来缩放现有的位图图像。
万一有人想尝试，这里是创建位图的代码：
public class BitmapMaker {
public static void main(String[] args) {
File dir = new File(File.separator + "test" + File.separator + "bitmap");
dir.mkdirs();
File f = new File(dir, "original.bmp");
File c = new File(dir, "copy.bmp");
buildBitmap(f);
}
public static void buildBitmap(File f) {
f.delete();
try(FileOutputStream fos = new FileOutputStream(f)){
fos.write(66);
fos.write(77);
fos.write(220);
fos.write(0);
fos.write(0);
fos.write(0);
fos.write(0);
fos.write(0);
fos.write(0);
fos.write(0);
fos.write(26);
fos.write(0);
fos.write(0);
fos.write(0);
fos.write(12);
fos.write(0);
fos.write(0);
fos.write(0);
fos.write(8);
fos.write(0);
fos.write(8);
fos.write(0);
fos.write(1);
fos.write(0);
fos.write(24);
fos.write(0);
for(int i = 0; i<64; i++) {
switch(i) {
case 2: case 3: case 4: case 5: case 9: case 14: case 16: case 19: case 20: case 23: case 24:
case 26: case 29: case 31: case 32: case 39: case 40: case 42: case 45: case 47: case 49: case 54:
case 58: case 59: case 60: case 61:
fos.write(0);
fos.write(0);
fos.write(0);
break;
case 0: case 1: case 6: case 7: case 8: case 15: case 48: case 55: case 56: case 57: case 62: case 63:
fos.write(255);
fos.write(255);
fos.write(255);
break;
default:
fos.write(0);
fos.write(200);
fos.write(0);
}
}
//1x2 bytes [ending nulls]
fos.write(0);
fos.write(0);
}catch(IOException e) {
e.printStackTrace();
}
}
}
错误：
Enter scale: 2
Original file size: 220
Scaled file size: 796
Scaled Length: 16
Scaled Width: 16
Bits per pixel: 3
bytes per scaled width: 48
counter - o - s - bArray[o]
1 --- 27 --- 27 --- -1
7 --- 28 --- 33 --- -1
13 --- 29 --- 39 --- -1
19 --- 30 --- 45 --- -1
25 --- 31 --- 51 --- -1
31 --- 32 --- 57 --- 0
37 --- 33 --- 63 --- 0
43 --- 34 --- 69 --- 0
43 --- 35 --- 123 --- 0
43 --- 36 --- 177 --- 0
43 --- 37 --- 231 --- 0
43 --- 38 --- 285 --- 0
43 --- 39 --- 339 --- 0
43 --- 40 --- 393 --- 0
43 --- 41 --- 447 --- 0
43 --- 42 --- 501 --- 0
43 --- 43 --- 555 --- 0
43 --- 44 --- 609 --- -1
43 --- 45 --- 663 --- -1
43 --- 46 --- 717 --- -1
43 --- 47 --- 771 --- -1
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 819
at test.BitmapResizer.main(BitmapResizer.java:107)