function dot(x,y) or pixel(x,y) missing ? about openvg

[ajstarks]

Note that this is a vector library, and pixel-level operations are usually not done at this level.
A possible workaround is to draw a rectangle or circle with the desired dimensions.

What is your application doing?

[tofrnr]

it's putting a series of function values
f(x) = y
in a coordinate system, shown as (x,y)

[ajstarks]

I suggest, picking the right scale for your app, and use circles to represent the points. See: https://github.com/ajstarks/openvg/blob/master/go-client/vgplot/vgplot.go for an example.

[tofrnr]

yes, but that's too much computation IMO
no idea, but perhaps
line (x,y,x,y) would also work, but that's already too much computation, too.

[ajstarks]

if you know the (x,y) coordinates, just place an appropriately sized circle.

[tofrnr]

yes, I understood your proposal, but as I said: too much computation to do.
It's a matter of execution speed:
There are about 10000-40000 points to draw each second.

[ajstarks]

With that throughput requirement you will need to pre-allocate the object and reuse using low-level OpenVG calls.

[tofrnr]

That's supposed to be too hard to understand to me, I just wanted to put single pixels by simple pixel(x,y) API calls.

[ajstarks]

There is a fork of the library that pre-allocates: https://github.com/paeryn/openvg/tree/newfonts

[tofrnr]

thank you, But there I also can't find a pixel(x,y) API function:

extern void Translate(VGfloat, VGfloat);
    extern void Rotate(VGfloat);
    extern void Shear(VGfloat, VGfloat);
    extern void Scale(VGfloat, VGfloat);
    extern void Text(VGfloat, VGfloat, const char *, Fontinfo, int);
    extern void TextMid(VGfloat, VGfloat, const char *, Fontinfo, int);
    extern void TextEnd(VGfloat, VGfloat, const char *, Fontinfo, int);
    extern VGfloat TextWidth(const char *, Fontinfo, int);
    extern void Cbezier(VGfloat, VGfloat, VGfloat, VGfloat, VGfloat, VGfloat, VGfloat, VGfloat);
    extern void Qbezier(VGfloat, VGfloat, VGfloat, VGfloat, VGfloat, VGfloat);
    extern void Polygon(VGfloat *, VGfloat *, VGint);
    extern void Polyline(VGfloat *, VGfloat *, VGint);
    extern void Rect(VGfloat, VGfloat, VGfloat, VGfloat);
    extern void Line(VGfloat, VGfloat, VGfloat, VGfloat);
    extern void Roundrect(VGfloat, VGfloat, VGfloat, VGfloat, VGfloat, VGfloat);
    extern void Ellipse(VGfloat, VGfloat, VGfloat, VGfloat);
    extern void Circle(VGfloat, VGfloat, VGfloat);
    extern void Arc(VGfloat, VGfloat, VGfloat, VGfloat, VGfloat, VGfloat);
    extern void Image(VGfloat, VGfloat, int, int, char *);
    extern void Start(int, int);
    extern void End();
    extern void SaveEnd(char *);
    extern void Background(unsigned int, unsigned int, unsigned int);
    extern void BackgroundRGB(unsigned int, unsigned int, unsigned int, VGfloat);
    extern void init(int *, int *);
    extern void finish();
    extern void setfill(VGfloat[4]);
    extern void setstroke(VGfloat[4]);
    extern void StrokeWidth(VGfloat);
    extern void Stroke(unsigned int, unsigned int, unsigned int, VGfloat);
    extern void Fill(unsigned int, unsigned int, unsigned int, VGfloat);
    extern void RGBA(unsigned int, unsigned int, unsigned int, VGfloat, VGfloat[4]);
    extern void RGB(unsigned int, unsigned int, unsigned int, VGfloat[4]);
    extern void FillLinearGradient(VGfloat, VGfloat, VGfloat, VGfloat, VGfloat *, int);
    extern void FillRadialGradient(VGfloat, VGfloat, VGfloat, VGfloat, VGfloat, VGfloat *, int);
    extern void ClipRect(VGint x, VGint y, VGint w, VGint h);
    extern void ClipEnd();
    extern Fontinfo loadfont(const int *, const int *, const unsigned char *, const int *, const int *, const int *,
                 const short *, int, int, int);
    extern void unloadfont(Fontinfo);
    extern void makeimage(VGfloat, VGfloat, int, int, VGubyte *);
    extern void saveterm();
    extern void restoreterm();
extern void rawterm();

[ajstarks]

As I said, substitute pixel(x,y), with Circle(x,y,size), where size is appropriately scaled to your canvas.
you could also use a Line(x, y, x+(unit), y) where unit the the appropriate size.

You will have to determine if the throughput is sufficient for your app.

[tofrnr]

yes, thank you, but I assumed it was easier to have a dedicated Pixel(x,y) or Dot(x,y) API function nevertheless
(Pixel size by StrokeWidth() size )