Q:

How to smoothly rasterize PDF using the API?

I'd like to rasterize a PDF source (in this case to PNG, 500x500 pixels) using these golang bindings for ImageMagick6. On the CLI, I can do this using
convert -density 5000 -define psd:fit-page=500x test.pdf -resize 500x test.png

which results in a smoothly rendered image.
What I'm failing to do right now is to produce something similar using the API: either the resulting image has scaled pixels or is blurry and has a size 500x500 pixels, or it's in the "original" size.
Here's a minimum snippet of my playground code:
package main

import "gopkg.in/gographics/imagick.v2/imagick"

func main() {
    imagick.Initialize()
    defer imagick.Terminate()
    mw := imagick.NewMagickWand()
    defer mw.Destroy()

    mw.SetImageResolution(5000,5000)
    mw.SetOption("psd:fit-page", "500x")

    mw.ReadImage("test.pdf")
    mw.ResizeImage(500, 500, imagick.FILTER_POINT, 1)
    mw.SetIteratorIndex(0) // This being the page offset
    mw.SetImageFormat("png")
    mw.WriteImage("test.png")
}

I got confused by density, image size, image resolution and canvas size I guess. How is it meant to be used?

A:

Your GO version of the convert command is missing the "density" argument. Replacing the call to SetImageResolution with one to SetOption and using a filter to smooth out the edges results in a smooth image:
package main

import "gopkg.in/gographics/imagick.v2/imagick"

func main() {
    imagick.Initialize()
    defer imagick.Terminate()
    mw := imagick.NewMagickWand()
    defer mw.Destroy()

    mw.SetOption("density", "5000")
    mw.SetOption("psd:fit-page", "500x")

    mw.ReadImage("test.pdf")

    mw.ResizeImage(500, 500, imagick.FILTER_LAGRANGE, 1)
    mw.SetIteratorIndex(0) // This being the page offset
    mw.SetImageFormat("png")
    mw.WriteImage("test.png")
}

