Failed to create thumbnail using the PTB_SaveAsImage function from the C API (In GO)

For testing the callas PDF toolbox SDK, I want to convert a sample PDF to a PNG. The callas license is activated. In my main() function, I successfully initialize the SDK. After that, I call the create method.

Here is my main() method:

func main() {
    log.SetOutput(os.Stdout)
    log.Println("Starting program")

    // Set up library path before initializing SDK
    setupLibraryPath()

    log.Println("Initializing SDK...")
    sdk, err := callas.NewCallasSDKWrapper()
    if err != nil {
        log.Printf("Failed to initialize SDK: %v\n", err)
        os.Exit(1)
    }
    defer func() {
        log.Println("Closing SDK...")
        if err := sdk.Close(); err != nil {
            log.Printf("Error closing SDK: %v", err)
        }
    }()

    // Verify that sample.pdf exists
    _, err = os.Stat("sample.pdf")
    if err != nil {
        log.Printf("Error: sample.pdf not found: %v", err)
        log.Println("Current directory contents:")
        files, _ := os.ReadDir(".")
        for _, file := range files {
            log.Printf("  %s", file.Name())
        }
        os.Exit(3)
    }

    log.Println("SDK initialized, creating thumbnail...")
    err = sdk.CreateThumbnail("sample.pdf", "sample.png", 80)
    if err != nil {
        log.Printf("Failed to create thumbnail: %v\n", err)
        os.Exit(2)
    }

    log.Println("Thumbnail created successfully")
}

Here are the logs:

2025/05/22 10:42:22 Creating thumbnail: converting 'sample.pdf' to 'sample.png' at resolution 80
2025/05/22 10:42:22 Calling PTB_SaveAsImage...
2025/05/22 10:42:22 Failed to create thumbnail: error code 8195
2025/05/22 10:42:22 Failed to create thumbnail: Failed to create thumbnail: error code 8195

Error code 8195 means: PTB_eerrFileDestFolderExist = 8195 / 0x2003 /

This is my create method:

// createThumbnail is a Go-friendly wrapper for creating a thumbnail.
func createThumbnail(pdfPath string, pngPath string, resolution int) error {
    log.Printf("Creating thumbnail: converting '%s' to '%s' at resolution %d", pdfPath, pngPath, resolution)

    cPdfPath := C.CString(pdfPath)
    defer C.free(unsafe.Pointer(cPdfPath))

    cPngPath := C.CString(pngPath)
    defer C.free(unsafe.Pointer(cPngPath))

    cResolution := C.uint(resolution)

    // Call the PTB_SaveAsImage function from the C API
    log.Println("Calling PTB_SaveAsImage...")
    result := C.PTB_SaveAsImage(
        (*C.PTB_Path_t)(unsafe.Pointer(cPdfPath)),
        C.PTB_ePNG, // Image format
        (*C.PTB_sys_char_t)(unsafe.Pointer(&cResolution)),
        C.PTB_eBaseline_Standard, // JPEG format (not applicable for PNG)
        C.PTB_eJPEG_low,          // Compression (not applicable for PNG)
        0,                        // First page
        0,                        // Last page (0 for all pages)
        (*C.PTB_Path_t)(unsafe.Pointer(cPngPath)),
        nil, // Callback function (optional)
        nil, // Callback user data
        nil, // Progress callback (optional)
        nil, // Progress callback user data
    )

    if result != C.PTB_eerrNone {
        errorMsg := fmt.Sprintf("Failed to create thumbnail: error code %d", result)
        log.Println(errorMsg)
        return fmt.Errorf(errorMsg)
    }

    log.Println("Thumbnail created successfully")
    return nil
}

The PTB_SaveAsImage function is comming from the C API of the callas SDK C-Libary.

Why do I get PTB_eerrFileDestFolderExist even though the output file path seems valid?