ImGui Image Fill / Imgui::Image() vs ImGui::GetWindowDrawList()->AddImage

Why can't the ImGui::Image() function fill the entire screen when it displays an image in the viewport, can the ImGui::GetWindowDrawList()->AddImage() function fill the entire screen??

using ImGui::GetWindowDrawList()->AddImage()

using ImGui::Image()

void CImGuiMgr::render_copyRTTex()
{
    Vec2 RenderResolution = CDevice::GetInst()->GetRenderResolution();
    Ptr<CTexture> pCopyTex = CRenderMgr::GetInst()->GetRTCopyTex();

    // current size
    ImVec2 vViewportSize = ImGui::GetContentRegionAvail();
    Vec2 vResolution = CDevice::GetInst()->GetRenderResolution();
    ImVec2 Resolution = { vResolution.x,vResolution.y };
    ImVec2 LeftTopUv;
    ImVec2 RightBottom;

    LeftTopUv.x = 0.0f;
    LeftTopUv.y = 0.0f;
    RightBottom.x = 1.0f;
    RightBottom.y = 1.0f;

    if (ImGui::Begin("Custom Image Viewer"))
    {
        float fContentAspectRatio = vViewportSize.x / vViewportSize.y;
        float fImageAspectRatio = RenderResolution.x / RenderResolution.y;

        if (fContentAspectRatio > fImageAspectRatio)
        {
            float imageWidth = vViewportSize.y * fImageAspectRatio;
            float xPadding = (vViewportSize.x - imageWidth) / 2;
            ImGui::SetCursorPosX(ImGui::GetCursorPosX() + xPadding);
            ImGui::Image(pCopyTex->GetSRV().Get(), ImVec2(imageWidth, vViewportSize.y), ImVec2(0, 0), ImVec2(1, 1));
        }
        // Scale the image vertically if the content region is taller than the image
        else
        {
            float imageHeight = vViewportSize.x / fImageAspectRatio;
            float yPadding = (vViewportSize.y - imageHeight) / 2;
            ImGui::SetCursorPosY(ImGui::GetCursorPosY() + yPadding);
            ImGui::Image(pCopyTex->GetSRV().Get(), ImVec2(vViewportSize.x, imageHeight), ImVec2(0, 0), ImVec2(1, 1));
        }



        // use image
        ImGui::SetNextWindowSize(vViewportSize);
        
        {
        // draw image
        ImGui::Image(pCopyTex->GetSRV().Get(), vViewportSize, LeftTopUv, RightBottom);
        }
    }
}

void CImGuiMgr::render_copyRTTex()
{
    Vec2 RenderResolution = CDevice::GetInst()->GetRenderResolution();
    Ptr<CTexture> pCopyTex = CRenderMgr::GetInst()->GetRTCopyTex();

    // current size
    ImVec2 vViewportSize = ImGui::GetContentRegionAvail();
    Vec2 vResolution = CDevice::GetInst()->GetRenderResolution();
    ImVec2 Resolution = { vResolution.x,vResolution.y };
    ImVec2 LeftTopUv;
    ImVec2 RightBottom;

    LeftTopUv.x = 0.0f;
    LeftTopUv.y = 0.0f;
    RightBottom.x = 1.0f;
    RightBottom.y = 1.0f;


    if (ImGui::Begin("Custom Image Viewer"))
    {
        ImGui::GetWindowDrawList()->AddImage(
            pCopyTex->GetSRV().Get(),
            ImGui::GetCursorScreenPos(),
            ImGui::GetWindowPos() + ImGui::GetWindowSize(),
            ImVec2(0, 0), ImVec2(1, 1));

        ImGui::End();

    }
}

2 case in here. '// use addimage' and '// use image'

When using the image() function, the above aspect ratio acquisition code was used.

I don't know why the motion is different.