How do I properly map a `MagImageScalingCallback` using JNA?

Question

I am using jna.jar, jna-3.2.5.jar and jna-3.3.0-platform.jar in my Java Project.

This is the Winapi function I want to replicate.

BOOL WINAPI MagImageScalingCallback(   _In_  HWND           hwnd,   _In_  void           *srcdata,   _In_  MAGIMAGEHEADER srcheader,   _Out_ void           *destdata,   _In_  MAGIMAGEHEADER destheader,   _In_  RECT           unclipped,   _In_  RECT           clipped,   _In_  HRGN           dirty ); 

This is my Java code

public interface MagImageScalingCallback extends StdCallLibrary.StdCallCallback{     public boolean MagImageScalingCallback(HWND hwnd,             Pointer srcdata,             MAGIMAGEHEADER.ByValue srcheader,             Pointer destdata,             MAGIMAGEHEADER.ByValue destheader,             RectByValue source,             RectByValue clipped,             HRGN dirty); } 

When I get into this method of the callback, I get unexpected results:

    public boolean MagImageScalingCallback(HWND hwnd, Pointer srcdata,             MAGIMAGEHEADER.ByValue srcheader, Pointer destdata,             MAGIMAGEHEADER.ByValue destheader, RectByValue source, RectByValue clipped, HRGN dirty) {         image.setRGB(0, 0, srcheader.width, srcheader.height, srcdata.getIntArray(0, srcheader.width * srcheader.height ), 0, srcheader.width);         return true;     } 

This table explains What works and what doesn't work in 32 bit and 64 bit system when I change the data type of the variables.

+--------------+--------------+-------------+-------------+ | Parameter    | Data type    |   64 bit    |   32 bit    | +--------------+--------------+-------------+-------------+ | source       | WinDef.RECT  |   Working   | Not Working | | clipped      | WinDef.RECT  |   Working   | Not Working | | source       | RectByValue  |   Working   |   Working   | | source       | RectByValue  |   Working   |   Working   | | srcdata      | Pointer      |   Working   | Not Working | | destdata     | Pointer      |   Working   | Not Working | +--------------+--------------+-------------+-------------+ 

Not working means a totally black image in the result

If I use the above code in a 64 bit system, I can capture the desktop(I can access the data from the Pointer variable). If I use the same code in 32 bit system, I am not getting any image. You can see my whole code

Why is the error in my code? How can I fix that?

For your Information. As you see in the screenSkip.java, Whenever MagSetWindowSource function is called. MagImageScalingCallback(in line 80) is called.

Problems in this section of code

If I run this code on a 64 bit system srcdata and destdata will hold the array of integer pixels of the Desktop(If I save this as image, it captures the desktop). But if I run the same code on 32 bit system these both variable array pixel value is always zero(If I save the image, it is always black)

64 bit system

32 bit system

@david-heffernan I am running this code on a 32-bit system. I know The Magnification API is not supported under WOW64;. Which means 32-bit magnification application works on a 32-bit system and 64-bit magnification application works on a 64-bit system. Please stop commenting that magnification API doesn't work on WOW64 and try to execute this code on a 32-bit system.

As for your request the below image shows the configuration of my System.

Answer 1

The callback is proper - there is no flaw in your code, besides you are using deprecated functions.

Consider using this:

try {     Rectangle screenRect = new Rectangle(Toolkit.getDefaultToolkit().getScreenSize());     BufferedImage  capture = new Robot().createScreenCapture(screenRect);     ImageIO.write(capture, "JPEG", new File("printed1.jpg")); } catch (Exception e) {     e.printStackTrace(); }