Help Needed: Resizing Images with Cairo in VB6

[tmighty2]

I'm using the Cairo graphics library in VB6 to work with PDFs by converting them to images for easier manipulation. My goal is to resize these images to a specific maximum width and height without losing the ability to view all details. However, I'm struggling with the resizing function using Cairo in VB6. Here's my attempt:

Public Function Resize(ByRef srf As cCairoSurface, ByVal uMaxWidth As Long, ByVal uMaxHeight As Long) As cCairoSurface
    Dim lNewWidth As Long
    Dim lNewHeight As Long
    
    ' Save original image for comparison
    srf.WriteContentToPngFile "d:\path\before_resize.png" (looks as expected)
    
    ' Calculate new dimensions
    ScaleImage srf.Width, srf.Height, uMaxWidth, uMaxHeight, lNewWidth, lNewHeight, scaleDownAsNeeded
    
    ' Create new resized image
    Dim nNew As cCairoSurface
    Set nNew = srf.CreateSimilar(CAIRO_CONTENT_COLOR_ALPHA, lNewWidth, lNewHeight, False)
    
    Dim Ctx As cCairoContext
    Set Ctx = nNew.CreateContext()
    
    ' Fill background (testing purposes)
    Ctx.SetSourceRGBA 1, 0.5, 1, 0.5 (creates a pink surface as expected)
    Ctx.Rectangle 0, 0, lNewWidth, lNewHeight
    Ctx.Fill
    
    ' Attempt to render resized content
    srf.CreateContext.RenderSurfaceContent nNew, 0, 0, 200, 200, CAIRO_FILTER_BEST, 0.5 (does not have any effect)
    
    ' Save resized image for comparison
    nNew.WriteContentToPngFile "d:\path\after_resize.png" 'shows a pink image only.
    
    ' Need assistance correcting my approach.
End Function

I'm not sure how to properly use the Cairo library for resizing images. Assistance in correcting my approach would be appreciated.

[jpbro]

It looks like you have your surfaces backwards - you want to create the context for nNew and write the surface content of srf to it:

    nNew.CreateContext.RenderSurfaceContent srf, 0, 0, 200, 200, CAIRO_FILTER_BEST, 0.5 (does not have any effect)

(I haven't tried it, so there might be other issues, but that one jumped out).

[tmighty2]

Thank you very much! That was my mistake. It works now.