Android把Bitmap保存为bmp图片

作者:燕歆波
导读: 把图片存成jpg和png来说相对简单，android提供了bitmap.compress（）方法可。但对于BMP这种格式的，并没有很好的办法；

找了很久，在网上找到了一个解决方式:
https://www.iteye.com/blog/coderlxl201209164551-1765740
提供两个可以参考的信息:
https://blog.csdn.net/wen0006/article/details/6195311
https://blog.csdn.net/q673327335/article/details/8432384

下面是保存为bmp图片的demo,根据文档来看,;

public static void save2Bmp(Bitmap bitmap){
        int w = bitmap.getWidth(), h = bitmap.getHeight();
        int[] pixels=new int[w*h];
        bitmap.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 {
            FileOutputStream fos = new FileOutputStream(EvidenceApplication.getContext().getExternalFilesDir("finger")+"/finger.bmp");
            fos.write(buffer);
            ZipUtil.zip(EvidenceApplication.getContext().getExternalFilesDir("finger")+"/finger.bmp",EvidenceApplication.getContext().getExternalFilesDir("finger")+"/finger.zip");
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
	
	/**
	*  文件头
	*/
    private static byte[] addBMPImageHeader(int size) {
        byte[] buffer = new byte[14];
        buffer[0] = 0x42;
        buffer[1] = 0x4D;
        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;
    }

    /**
     * 文件信息头
     * @param w
     * @param h
     * @return
     */
    private static byte[] addBMPImageInfosHeader(int w, int h) {
        byte[] buffer = new byte[40];
        buffer[0] = 0x28;
        buffer[1] = 0x00;
        buffer[2] = 0x00;
        buffer[3] = 0x00;
        buffer[4] = (byte) (w >> 0);
        buffer[5] = (byte) (w >> 8);
        buffer[6] = (byte) (w >> 16);
        buffer[7] = (byte) (w >> 24);
        buffer[8] = (byte) (h >> 0);
        buffer[9] = (byte) (h >> 8);
        buffer[10] = (byte) (h >> 16);
        buffer[11] = (byte) (h >> 24);
        buffer[12] = 0x01;
        buffer[13] = 0x00;
        buffer[14] = 0x18;
        buffer[15] = 0x00;
        buffer[16] = 0x00;
        buffer[17] = 0x00;
        buffer[18] = 0x00;
        buffer[19] = 0x00;
        buffer[20] = 0x00;
        buffer[21] = 0x00;
        buffer[22] = 0x00;
        buffer[23] = 0x00;
        buffer[24] = (byte) 0xE0;
        buffer[25] = 0x01;
        buffer[26] = 0x00;
        buffer[27] = 0x00;
        buffer[28] = 0x02;
        buffer[29] = 0x03;
        buffer[30] = 0x00;
        buffer[31] = 0x00;
        buffer[32] = 0x00;
        buffer[33] = 0x00;
        buffer[34] = 0x00;
        buffer[35] = 0x00;
        buffer[36] = 0x00;
        buffer[37] = 0x00;
        buffer[38] = 0x00;
        buffer[39] = 0x00;
        return buffer;
    }
	
    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 * 3];
        int offset=0;
        for (int i = len-1; i>=w; i-=w) {
            //DIB文件格式最后一行为第一行，每行按从左到右顺序
            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);
                offset += 3;
            }
        }
        return buffer;
    }