[Lazarus] using a weird DLL

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I would like to use a function exported from a DLL. The DLL was written in C++ (Visual Studio 2015).

Inside the original code the function is declared as 

        public bool GetSkinFeatures(Bitmap Input_Bitmap, Rectangle ROI_Rect, double[] ExtractedFeatures)

Anybody knows how to use it from Lazarus?

This is too much for me...

Thank you

Duilio

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duilio foschi via lazarus <[hidden email]> schrieb am So., 31. Jan. 2021, 23:23:

I would like to use a function exported from a DLL. The DLL was written in C++ (Visual Studio 2015).

Inside the original code the function is declared as 

        public bool GetSkinFeatures(Bitmap Input_Bitmap, Rectangle ROI_Rect, double[] ExtractedFeatures)

Anybody knows how to use it from Lazarus?

Can you also show the declarations of Bitmap and Rectangle? Is the function declared inside an "extern "C"" block? 

Regards, 

Sven 

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for Sven:

>Is the function declared inside an "extern "C"" block? 

no

The code says:

using System;

using System.Collections.Generic;

using System.Linq;

using System.Text;

using System.Threading.Tasks;

using System.Runtime.InteropServices;

using System.Drawing;

using System.Drawing.Imaging;

namespace SkinAnalyzer

{

    public class ImageProcessing

    {

        //--------------------------------------------------------------------------------------------

        public ImageProcessing()

        {

            // init., if necessary

        }

        //--------------------------------------------------------------------------------------------

        // get the features

        public bool GetSkinFeatures(Bitmap Input_Bitmap, Rectangle ROI_Rect, double[] ExtractedFeatures)

        {

            // check the parameters

            if (Input_Bitmap == null)

                return false;

            if (Input_Bitmap.PixelFormat != PixelFormat.Format8bppIndexed &&

                    Input_Bitmap.PixelFormat != PixelFormat.Format24bppRgb &&

                    Input_Bitmap.PixelFormat != PixelFormat.Format32bppArgb &&

                    Input_Bitmap.PixelFormat != PixelFormat.Format32bppRgb)

                return false;

            // get the input pixels

            Rectangle rect1 = new Rectangle(0, 0, Input_Bitmap.Width, Input_Bitmap.Height);

            BitmapData input_data = Input_Bitmap.LockBits(rect1, ImageLockMode.ReadOnly, Input_Bitmap.PixelFormat);

            IntPtr ptr1 = input_data.Scan0;

            int bytesbpp = 0;    // bytes_per_pixel

            switch (Input_Bitmap.PixelFormat)

            {

On Mon, Feb 1, 2021 at 10:08 AM duilio foschi <[hidden email]> wrote:

I am corrected. The DLL is written in c#. It seems that Bitmap and Rectangle are common predefined/usable objects in C#.

Re Bitmap, I found these notes:
"Surely you cannot expect C# Bitmap to be binary compatible with Delphi TBitmap? You need to pass around an HBITMAP. On the Delphi side you use ReleaseHandle to get the HBITMAP. On the C# side it would be Image.FromHbitmap"

Re Rectangle, I found nothing interesting :(

However it seems natural to expect that Rectangle it is given by a pointer to a fixed array of 2 points= 4 integers= 16 bytes in all.

Thank you
Duilio

On Mon, Feb 1, 2021 at 7:52 AM Sven Barth <[hidden email]> wrote:

duilio foschi via lazarus <[hidden email]> schrieb am So., 31. Jan. 2021, 23:23:

I would like to use a function exported from a DLL. The DLL was written in C++ (Visual Studio 2015).

Inside the original code the function is declared as 

        public bool GetSkinFeatures(Bitmap Input_Bitmap, Rectangle ROI_Rect, double[] ExtractedFeatures)

Anybody knows how to use it from Lazarus?

Can you also show the declarations of Bitmap and Rectangle? Is the function declared inside an "extern "C"" block? 

Regards, 

Sven 

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duilio foschi via lazarus <[hidden email]> schrieb am Mo., 1. Feb. 2021, 11:22:

On Mon, Feb 1, 2021 at 10:08 AM duilio foschi <[hidden email]> wrote:

I am corrected. The DLL is written in c#. It seems that Bitmap and Rectangle are common predefined/usable objects in C#.

You can't trivially use a C# (or .NET in general) library in native code. (It essentially involves hosting the CLR and then invoking the code) 

RemObjects for example provides bridges for the managed and unmanaged code, but I don't know whether it supports Lazarus and it isn't free (as in beer) anyway. ( https://hydra.remobjects.com/hydra/default.aspx ) 

Regards, 

Sven 

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