[cairo] Trying to figure out some rasterization problems
behdad at behdad.org
Sun Apr 21 08:29:28 PDT 2013
On 13-04-21 11:13 AM, David Kastrup wrote:
>>> >> Unfortunately, it _does_ make a difference. Why do we care? Because
>>> >> note stems are rectangles with rounded corners. Not completely circular
>>> >> stroke ends, just rounded corners. If we care for stroke adjustment
>>> >> (which we do), that means our actual shape needs to be represented as an
>>> >> intersection of a stroke-adjusted rectangle and clipping off the rounded
>>> >> corners. That clipping apparently removes too much. An easy solution
>>> >> appears to be to restroke the middle part of the rectangle without any
>>> >> clipping. Which comes to problem b) which I think Cairo might be
>>> >> responsible for:
>> > I still have no idea what you are talking about. Perhaps some images
>> > would help?
> What's wrong with "a rectangle with rounded corners"? At any rate,
> stroke adjustment deals with rasterization on a black&white device: if
> you have a thin line, the normal PostScript/PDF way is to color all
> pixels black that have any part inside covered by the filled/stroked
> region. For thin lines, this adds up to one line of blackness too much
> on each side. Stroke adjustment checks the total width and reduces it
> (starting on the side with the larger overhang) by 1 pixel until it is
> not off more than half a pixel. So 0, 1 or two pixels are culled from
> the width, depending on where it lies in the rasterization.
Ok, it makes more sense now.
But I have to ask: in 2013, who cares about stroke adjustment? Just draw a
shape and fill it. I'm sure no print would look bad.
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