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