I would like to demo the Histogram Effect but the output is blank I’ve tried a Sofware type and Hardware type render target but the results are the same. Ive also tried ensuring that the effect’s input bitmap is the same width as the bins if that is a requirement. No hr error is reported after EndDraw().

Is there something else that is required for the Histogram effect or is there something in this code that needs to be fixed?

bool Display_Demo_Effect(ID2D1RenderTarget *arg_render_tgt, CLSID arg_clsid = CLSID_D2D1Histogram)
{
    // DBG_TRACKER_FUNCTION_NAME_T;

    if (!arg_render_tgt) { return false; }

    if (arg_clsid == CLSID_NULL) { return false; }

    CComPtr<ID2D1DeviceContext>      ccptr_dvctxt = nullptr;
    CComPtr<ID2D1BitmapRenderTarget> ccptr_bitmap_tgt = nullptr;
    CComPtr<ID2D1SolidColorBrush>    ccptr_brush_sc = nullptr;
    CComPtr<ID2D1Bitmap>             ccptr_bitmap = nullptr;
    CComPtr<ID2D1Effect>             ccptr_demo_effect = nullptr;

    HRESULT hr = S_OK;

    bool alt_bmp_method = false;

    arg_render_tgt->QueryInterface(&ccptr_dvctxt);

    if (!ccptr_dvctxt) { /* Error Message */ return false; }

    if (alt_bmp_method)
    {
        // Match the default bins count
        D2D1_SIZE_F des_sz_f = { 256.0f, 256.0f };

        D2D1_SIZE_U des_sz_u = { 256, 256 };

        hr = ccptr_dvctxt->CreateCompatibleRenderTarget(des_sz_f, des_sz_u, &ccptr_bitmap_tgt);
    }
    else
    {
        // Default creation method
        hr = ccptr_dvctxt->CreateCompatibleRenderTarget(&ccptr_bitmap_tgt);
    }

    if (FAILED(hr)) { /* Error Message */ return false; }

    D2D1_COLOR_F demo_colr = { 0.45f, 0.56f, 0.72f, 0.66f };
    
    D2D1_COLOR_F clr_colr  = { 0.5f, 0.5f, 0.5f, 1.0f };

    D2D1_ELLIPSE demo_ellipse = D2D1::Ellipse
    (
        D2D1::Point2F(128.0f, 128.0f),
        100.0f,
        100.0f
    );

    hr = ccptr_bitmap_tgt->CreateSolidColorBrush(demo_colr, &ccptr_brush_sc);

    if (FAILED(hr)) { /* Error Message */ return false; }

    // Draw an Ellipse on the bitmap
    ccptr_bitmap_tgt->BeginDraw();

    hr = ccptr_bitmap_tgt->Flush();
    
    ccptr_bitmap_tgt->Clear( {0.0f, 0.0f, 0.0f, 0.0f} );
    
    ccptr_bitmap_tgt->FillEllipse(&demo_ellipse, ccptr_brush_sc);
    
    hr = ccptr_bitmap_tgt->EndDraw();

    if (FAILED(hr)) { /* Error Message */ return false; }

    // Expose the bitmap
    ccptr_bitmap_tgt->GetBitmap(&ccptr_bitmap);

    if (FAILED(hr)) { /* Error Message */ return false; }

    hr = ccptr_dvctxt->CreateEffect(arg_clsid, &ccptr_demo_effect);

    if (FAILED(hr)) { /* Error Message */ return false; }
    
    // Configure the effect's input
    ccptr_demo_effect->SetInput(0, ccptr_bitmap);

    // Special considerations for Histogram
    if (arg_clsid == CLSID_D2D1Histogram)
    {
        UINT32 parm_bins = 256;

        ccptr_demo_effect->SetValue(D2D1_HISTOGRAM_PROP_NUM_BINS, parm_bins);

        ccptr_demo_effect->SetValue(D2D1_HISTOGRAM_PROP_CHANNEL_SELECT, D2D1_CHANNEL_SELECTOR_G);

        D2D1_RECT_F inp_local_rc = { 0.0f };
        D2D1_RECT_F out_local_rc = { 0.0f };

        D2D1_SIZE_F inp_sz = { 0.0f };
        D2D1_SIZE_F out_sz = { 0.0f };

        CComPtr<ID2D1Image>  ccptr_inp_image = nullptr;
        CComPtr<ID2D1Image>  ccptr_out_image = nullptr;

        ccptr_demo_effect->GetInput(0, &ccptr_inp_image);
        ccptr_demo_effect->GetOutput(&ccptr_out_image);
        
        // Display the input image local bounds
        if (ccptr_inp_image)
        {
            hr = ccptr_dvctxt->GetImageLocalBounds(ccptr_inp_image, &inp_local_rc);

            inp_sz = 
            { 
                fabsf(inp_local_rc.right  - inp_local_rc.left), 
                fabsf(inp_local_rc.bottom - inp_local_rc.top) 
            };

            // DisplayRC_Via_MsgBox(inp_local_rc);
            // DisplaySZ_Via_MsgBox(inp_sz);
        }

        if (ccptr_out_image)
        {
            hr = ccptr_dvctxt->GetImageLocalBounds(ccptr_out_image, &out_local_rc);

            out_sz =
            {
                fabsf(out_local_rc.right  - out_local_rc.left),
                fabsf(out_local_rc.bottom - out_local_rc.top)
            };

            // DisplayRC_Via_MsgBox(out_local_rc);
            // DisplaySZ_Via_MsgBox(out_sz);
        }
    }

    // Prove the dvctxt and input bitmap are valid
    ccptr_dvctxt->BeginDraw();
    hr = ccptr_dvctxt->Flush();
    ccptr_dvctxt->Clear(clr_colr);
    ccptr_dvctxt->DrawImage(ccptr_bitmap);
    hr = ccptr_dvctxt->EndDraw();

    if (FAILED(hr)) { /* Error Message */ return false; }

    Sleep(3000);

    // Display the Effect: nothing is drawn
    ccptr_dvctxt->BeginDraw();
    hr = ccptr_dvctxt->Flush();
    ccptr_dvctxt->Clear(clr_colr);
    ccptr_dvctxt->DrawImage(ccptr_demo_effect);
    hr = ccptr_dvctxt->EndDraw();

    // No failure even though nothing is displayed

    if (FAILED(hr)) { /* Error Message */ return false; }

    Sleep(3000);

    // Clear the window
    ccptr_dvctxt->BeginDraw();
    hr = ccptr_dvctxt->Flush();
    ccptr_dvctxt->Clear( {0.0f, 0.0f, 0.0f, 0.0f} );
    hr = ccptr_dvctxt->EndDraw();

    return true;
}

This code works with single input effects except the Histogram Effect. ChatGPT just regurgitates the same code on the MSDN example; however it did mention to check here on stack overflow. I could not find any other examples for CLSID_D2D1Histogram using a google search. I’ve tried ensuring that the render target is Hardware Type and feature level 10 or Software Type but the results are the same; the output image local bound rectangle is {0} and nothing is displayed