| Author | Message | |||
     Dieter Mayr New member Username: Dieter_mayr Post Number: 14 Registered: 11-2004 |
Im using Fan transformation quiet often for making a concave or convex text for my images. Jonathan, do u see a possibility to expand the range of Curvature ? Maybe even to negative values, means to get a bow in the other direction ? Now i make it this way, to mirror my text, use fan, and mirror it back. What i dont understand now, is the math behind Curvature. First i thought, 100% means an angel of 1 rad, abt 57 deg, wich looks right with and landscape oriented picture, but when use with a portrait oriented picture, the angle is much smaller. Would be very nice if you could explain, please, what a Curvature of 100% means. Thank you, and greetings from Salzburg Dieter | |||
| Jonathan Sachs Board Administrator Username: Admin Post Number: 2257 Registered: 08-2002 |
Running text along a curve was not what I had originally imagined for Fan, but it sounds like a good idea. The formula for min and max angle and radius are: r = 100.0*ny/curvature; thetamax = 0.5*nx/r; thetamin = -thetamax; rmin = abs(r - 0.5*ny); rmax = abs(r + 0.5*ny); where nx and ny are the image width and height in pixels. I don't remember why I selected this formula any more. What this means is that the radius of curvature of the circle that passes through the horizontal centerline of the image is proportional to the height of the image. Jonathan Sachs Digital Light & Color | |||
| Dieter Mayr New member Username: Dieter_mayr Post Number: 15 Registered: 11-2004 |
Jonathan, thanks for your information. Im a fan of cuved text, and i use it quiet often, for titels of albums or so. I have, based on your formulas, written a little excel sheet, to calcuate the angle by given curvature, or to calculate the curvature by given angle. I send it to you per email, so if you want, please feel free to make it available to the public. Greetings from Salzburg Dieter | |||
| Jonathan Sachs Board Administrator Username: Admin Post Number: 2259 Registered: 08-2002 |
Here is Dieter's spreadsheet. It computes the angle resulting from a given curvature slider setting or vice versa.
Jonathan Sachs Digital Light & Color | |||
| Kevin Elliott New member Username: Kevgermany Post Number: 63 Registered: 09-2004 |
I tried the fan transform, hadn't got around to it before. I was trying to create a complete circular fan from a panoramic to use as an emblem for a T-shirt. Setting it at 100% caused PWP to crash. By the time the fan values reached 50% there was clipping on the sides, and the base of the image wasn't even (the right leg was lower than the left). It looks as if I'd be able to get around these by splitting the the original, doing 2 50% fans, then recombining, but it's a lot of messing. I've been trying to convince a friend to switch to PWP from PS-CS, this is one thing he couldn't do in PS, so what I was able to do was quite impressive, but not quite good enough. Any better work-arounds? Kev | |||
| Dieter Mayr New member Username: Dieter_mayr Post Number: 18 Registered: 11-2004 |
Kevin, i played around with your problem. I made a rectangle 1000 * 160 pixels, wich should, according to jonathans fromulas, give a angle of nearly 360° at 100 % curvature. Up to 50% everything works fine, and i get a 180° bow at 50%. But when going higher, the image is clipped and not symetrical, as you described. So it looks to me that it is not possible to create a bow bigger the 180°, without clipping. The only way i see is, as you described, to put together two 180 bows. Dieter | |||
| Kevin Elliott New member Username: Kevgermany Post Number: 64 Registered: 09-2004 |
Dieter, Thanks. This could be used for creating logos, cd labels and so on. The original was about 10 000 pixels wide, and looked a little clipped on the right at 50%. Now if we could just specify the radius, centre, angle as well as % and get the bugs out, we'd be there. Grüße Kevin | |||
| Dieter Mayr New member Username: Dieter_mayr Post Number: 19 Registered: 11-2004 |
Kevin, Jonathan, My preference for a improofed Fan transformation would be: The length of circumference of the centerline = the width of the image, to minimize distortion. Angle adjustable from 0° (unchanged image) to 360° (full circle). The ability to make concave and convex bows. I dont know if a adjustable centre and radius is usefull, but if one knows a usage for it, its ok for me ;). Greetings from Salzburg Dieter | |||
| Kevin Elliott New member Username: Kevgermany Post Number: 65 Registered: 09-2004 |
Dieter, I'm with you mostly. What I was really looking for was to be able to take an image, make it into an arc, without worrying too much about how big it was to start with. With your approach we'd need to do the maths, then resize, then fan. Leads to more difficulty in use and more degradation. I think we'd be able to do what you require just by specifying radii for the inner circle (blank), outer circle(outer edge) and degrees. I'd imagine a radial bicubic interpolation with sharpening would also be necessary. | |||
| Dieter Mayr New member Username: Dieter_mayr Post Number: 21 Registered: 11-2004 |
Your right, Kevin, we should let the math do our computers. As i see it, it would be necesary to specify the radii and angle, then get a sort of crop rectangle with the needet witdh/hight ratio to specify the area of the picture to be bend into the desired arc. Lets see what others, especially Jonathan, thinks of that. Dieter |
Fan.xls