bitmap转bmp图片格式

[android]代码库
public class FileSaver {
    public static final String dir = "Text2Img";
    public static final String ACCESS_ERROR = "access_error";
    public static final String FILE_ERROR = "file_error";
    public static final String SAVE_ERROR = "save_error";
 
    public static String saveFileHighQuality(Bitmap bm) {
        String fileName = new SimpleDateFormat("yyyyMMddhhmmss").format(new Date()) + ".bmp";
        if(!Environment.MEDIA_MOUNTED.equals(Environment.getExternalStorageState())) {
            return ACCESS_ERROR;
        }
        File file = new File(Environment.getExternalStorageDirectory() + File.separator + dir
                             + File.separator + fileName);
        System.out.println(file.getPath());
        if(!file.getParentFile().exists()) {
            file.getParentFile().mkdirs();
        }
        FileOutputStream out = null;
        try {
            out = new FileOutputStream(file);
        } catch (FileNotFoundException e) {
            e.printStackTrace();
            return FILE_ERROR;
        }
 
 
        int w = bm.getWidth();
        int h = bm.getHeight();
        int[] pixels = new int[w * h];
        bm.getPixels(pixels, 0, w, 0, 0, w, h);
 
        byte[] rgb = addBMP_RGB_888(pixels, w, h);
        byte[] header = addBMPImageHeader(rgb.length);
        byte[] infos = addBMPImageInfosHeader(w, h);
 
 
        byte[] buffer = new byte[54 + rgb.length];
        System.arraycopy(header, 0, buffer, 0, header.length);
        System.arraycopy(infos, 0, buffer, 14, infos.length);
        System.arraycopy(rgb, 0, buffer, 54, rgb.length);
        try {
            out.write(buffer);
            out.flush();
            out.close();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
            return SAVE_ERROR;
        }
        return file.getPath();
    }
 
    private static byte[] addBMP_RGB_888(int[] b, int w, int h) {
        int len = b.length;
        System.out.println(b.length);
        byte[] buffer = new byte[w * h * 4];
        int offset = 0;
        for (int i = len - 1; i >= w; i -= w) {
            int end = i, start = i - w + 1;
            for(int j = start; j <= end; j++) {
                buffer[offset] = (byte)(b[j] >> 0);
                buffer[offset + 1] = (byte)(b[j] >> 8);
                buffer[offset + 2] = (byte)(b[j] >> 16);
                buffer[offset + 3] = (byte)(b[j] >> 24);
                offset += 4;
            }
        }
        return buffer;
    }
 
    //BMP文件信息头
    private static byte[] addBMPImageInfosHeader(int w, int h) {
        byte[] buffer = new byte[40];
        //这个是固定的 BMP 信息头要40个字节
        buffer[0] = 0x28;
        buffer[1] = 0x00;
        buffer[2] = 0x00;
        buffer[3] = 0x00;
        //宽度 地位放在序号前的位置 高位放在序号后的位置
        buffer[4] = (byte) (w >> 0);
        buffer[5] = (byte) (w >> 8);
        buffer[6] = (byte) (w >> 16);
        buffer[7] = (byte) (w >> 24);
        //长度 同上
        buffer[8] = (byte) (h >> 0);
        buffer[9] = (byte) (h >> 8);
        buffer[10] = (byte) (h >> 16);
        buffer[11] = (byte) (h >> 24);
        //总是被设置为1
        buffer[12] = 0x01;
        buffer[13] = 0x00;
        //比特数 像素 32位保存一个比特 这个不同的方式(ARGB 32位 RGB24位不同的!!!!)
        buffer[14] = 0x20;
        buffer[15] = 0x00;
        //0-不压缩 1-8bit位图
        //2-4bit位图 3-16/32位图
        //4 jpeg 5 png
        buffer[16] = 0x00;
        buffer[17] = 0x00;
        buffer[18] = 0x00;
        buffer[19] = 0x00;
        //说明图像大小
        buffer[20] = 0x00;
        buffer[21] = 0x00;
        buffer[22] = 0x00;
        buffer[23] = 0x00;
        //水平分辨率
        buffer[24] = 0x00;
        buffer[25] = 0x00;
        buffer[26] = 0x00;
        buffer[27] = 0x00;
        //垂直分辨率
        buffer[28] = 0x00;
        buffer[29] = 0x00;
        buffer[30] = 0x00;
        buffer[31] = 0x00;
        //0 使用所有的调色板项
        buffer[32] = 0x00;
        buffer[33] = 0x00;
        buffer[34] = 0x00;
        buffer[35] = 0x00;
        //不开颜色索引
        buffer[36] = 0x00;
        buffer[37] = 0x00;
        buffer[38] = 0x00;
        buffer[39] = 0x00;
        return buffer;
    }
 
    //BMP文件头
    private static byte[] addBMPImageHeader(int size) {
        byte[] buffer = new byte[14];
        //magic number 'BM'
        buffer[0] = 0x42;
        buffer[1] = 0x4D;
        //记录大小
        buffer[2] = (byte) (size >> 0);
        buffer[3] = (byte) (size >> 8);
        buffer[4] = (byte) (size >> 16);
        buffer[5] = (byte) (size >> 24);
        buffer[6] = 0x00;
        buffer[7] = 0x00;
        buffer[8] = 0x00;
        buffer[9] = 0x00;
        buffer[10] = 0x36;
        buffer[11] = 0x00;
        buffer[12] = 0x00;
        buffer[13] = 0x00;
        return buffer;
    }
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