java - 将/assets/image.png 转换为 byte[]

Question

如何将/assets/image.png 转换为 byte[] ？

我试过那样(基于在 SO 上找到的解决方案):

public void printimage(View view) {
    AssetManager assetManager = getAssets();
    InputStream inputStream = null;

    try {
        inputStream = assetManager.open("logo_print.png");
        byte[] bytesLogo = IOUtils.toByteArray(inputStream);

        int ret = printer.printImage(bytesLogo);

        if (ret < 0) {
            Toast(context, "printimage fail");
        }
        Toast(context, "image printed :)");

    }
    catch (IOException e){
        Log.e("message: ", e.getMessage());
        Toast(context, "printimage: convert image to Bytes fail");
    }
}

printImage — 在包中声明如下:

public class Cprinter {
    public native int printImage(byte[] bytes);
}

但是应用程序在打印 printimage() 时崩溃，错误是“找不到 native 方法:android.pt.Cprinter.printImage:([B)I”

我已将字节转换为字符串 (bytesLogo.toString())，每次执行此命令都会返回不同的结果:“[B@40d7c798”、“[B@40d848e0”、“[B@40d59ff0”等.

目的: 我有一个带有内部收据打印机的安卓设备。供应商提供了用于为设备开发自己的软件的库 (libfile.so) 和示例源。打印简单的文本没问题，但我在打印图像( Logo )时遇到了麻烦。

Here is the vendors` tiny documentation.

p.s:我是Java新手。

Answer 1

试试这个

   InputStream inputStream = getAssets().open("logo_print.png");

    byte[] buffer = new byte[8192];
    int bytesRead;
    ByteArrayOutputStream output = new ByteArrayOutputStream();
    while ((bytesRead = inputStream.read(buffer)) != -1) {
        output.write(buffer, 0, bytesRead);
    }
    byte file[] = output.toByteArray();

字节数组包含

1B 2A n ml mh converted data 1B 4A 00

1B 2A -- begin the block

n - printing mode
  a) Q110 support 4 kinds of printing modes,as follow：

    n=0x21: 24-point double-density;

    n=0x20: 24-point single-density;

    n=0x01: 8-point double-density;

    n=0x00: 8-point single-density；

  b) NXP only support n=0x21: 24-point double-density;

converted data

1B 4A 00 end the block and execute print (print start)

像聪明人一样

byte[0] = 0x1B;
byte[1] = 0x2A;
byte[2] = 0x21; // 24-point double-density;

and so on...