Screencap is generating corrupted PNG files

[ilpersi]

Describe the bug
When I run the snippet below the generated PNG file is corrupted.

try (FileOutputStream outputStream = new FileOutputStream(aDevice.toString().replace(":", "")+".png")) {
    stdout = aDevice.executeShell("screencap", "-p");
    Stream.copy(stdout, outputStream);
}

The script is taken from the examples:

jadb/test/se/vidstige/jadb/test/integration/RealDeviceTestCases.java

Line 112 in fedca18

public void testScreenshot() throws Exception {

No error is raised during the run time.

I am able to correctly generate png file from the command prompt using a standard command like this:

adb.exe -s 127.0.0.1:5555 exec-out screencap -p > test.png

To Reproduce
Steps to reproduce the behavior:

1. Below you can find the full example class with the whole example code
2. I am using Bluestacks emulator to perform the tests
3. Run the code
4. Check the generated PNG

Expected behavior
The generated file is a valid PNG.

Screenshots
Hex dump of the corrupted file generated via jadb

Hex dump of the correct file generated via command line

You can notice differences starting from byte number 4 (value is 0d instead of 0a).

Other Notes
Apparently this is a know issue and I've found a relevant topic in stack overflow.
https://stackoverflow.com/questions/13578416/read-binary-stdout-data-like-screencap-data-from-adb-shell

Suggestion there is to use exec-out command, but apparently I am not able to make it work with jdb. Looking into open issues, this may be related to #149 and #150.

Desktop (please complete the following information):

• OS: Windows 11
• Version 1.2.1
• Java 17.0.1

Full class source

package org.example;

import se.vidstige.jadb.*;


import java.io.*;
import java.net.InetSocketAddress;
import java.util.List;


public class Main {

    public static void main(String[] args) {

        // we launch the ADB Server
        try {
            new AdbServerLauncher(new Subprocess(), "D:\\Android\\SDK\\platform-tools\\adb.exe").launch();
        } catch (IOException e) {
            throw new RuntimeException(e);
        } catch (InterruptedException e) {
            System.out.println("AdbServerLauncher InterruptedException: " + e);
        }

        // We connect to the right device
        JadbConnection jadb = new JadbConnection();
        try {
            jadb.connectToTcpDevice(new InetSocketAddress("127.0.0.1", 5555));
        } catch (IOException e) {
            System.out.println("connectToTcpDevice IOException: " + e);
        } catch (JadbException e) {
            System.out.println("connectToTcpDevice JadbException: " + e);
        } catch (ConnectionToRemoteDeviceException e) {
            System.out.println("connectToTcpDevice ConnectionToRemoteDeviceException: " + e);
        }

        try {
            List<JadbDevice> devices = jadb.getDevices();
            devices.forEach(aDevice -> {
                System.out.println(aDevice.toString());

                // https://github.com/vidstige/jadb/blob/fedca18ae1ca3e5167487f737e48877939ca8dc7/test/se/vidstige/jadb/test/integration/RealDeviceTestCases.java#L112
                InputStream stdout;
                try {
                    try (FileOutputStream outputStream = new FileOutputStream(aDevice.toString().replace(":", "")+".png")) {
                        stdout = aDevice.executeShell("screencap", "-p");
                        Stream.copy(stdout, outputStream);
                    }

                } catch (IOException e) {
                    System.out.println("FileOutputStream IOException: " + e);
                } catch (JadbException e) {
                    System.out.println("FileOutputStream JadbException: " + e);
                }

            });
        } catch (IOException e) {
            throw new RuntimeException(e);
        } catch (JadbException e) {
            System.out.println(e.getMessage());
        }


    }
}

[vidstige]

Thanks for this very detailed issue report. I didn't notice it until right now. I don't have time to look into it currently, and it seems none of the maintainers don't either. It seems like a very nice thing to add though!

I don't currently have java development setup with and IDE and Android emulator, etc. But if someone would like to look into it, that would be great. I would be glad to help in any way I can as I know my way around the source code in this project.