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Re: about contibuting to octave

From: Ben Abbott
Subject: Re: about contibuting to octave
Date: Thu, 12 Mar 2009 17:46:46 +0800

On Mar 12, 2009, at 5:02 PM, Michael Goffioul wrote:

On Thu, Mar 12, 2009 at 8:53 AM, Ben Abbott <address@hidden> wrote:

On Mar 11, 2009, at 2:37 PM, xianghang liu wrote:

Two functions below are two methods of computing bounding box of a text object. I wrote them following algorithms used in GD and Freetype. Only a slight diiference is between them. It is the computation of bounding box of a charachter. And the final result of them are slightly different as well.
Please tell me if you find any mistakes or have suggestions.

I'm confused by what is meant by "bounding box", and as I'm unfamiliar with FreeType (and have poor c++ skills) I'm uncertain that this implementation will result in what is expected for the text object property, "extent".

Consider the three examples below (from Matlab).

h1 = text(0,0,'_','interpreter','none','units','points','fontsize',12); h2 = text(0,0,'|','interpreter','none','units','points','fontsize',12); h3 = text(0,0,'-','interpreter','none','units','points','fontsize',12);

ans =

           0         -8.8          8.8           16


ans =

           0         -8.8          5.6           16


ans =

           0         -8.8          6.4           16

The choice of character only impacts the width of the extent. The lower left
corner and height of the extent is constant.

I guess y and h (assuming the extent is [x y w h]) are
considered constant for a given font and computed from the
font ascent, descent and height ((0,0) being the baseline).
While the width is string dependent.

Does the extent takes the margin property into account?


No, the margin is in addition to the extent. The margin+extent is used to define the region filled by backgroundcolor, or the region surrounded by edgecolor.

The extent info may be used to position string relative to other objects (alignment for example), and I assume to even concatenate strings.


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