Can an image be shaped to an arc?

Sc00by5ting · **Joined:** Aug 12, 2014 **Posts:** 29

saulgoode wrote:

Here is the result I achieved using your images (I slightly cropped the decal to eliminate the white border around it):

[ Image ]

The XCF file can be downloaded from the following webpage:
http://barn.kerosenecow.net/u/saul/m/michelin-xcf-d7d2/

Before starting, I first scaled the tire image so that the tire was 139mm in diameter at 300 DPI.

I then created a selection around the outer circumference of the "whitewall" and noted it was 1526 pixels in diameter. I then created a selection around the inner circumference and measured the thickness of the "whitewall" to be 91 pixels.

I scaled the decal image to be 1103x182 pixels (actually I just changed the height, the width of 1103 was automatically calculated to maintain the same aspect ratio).

Next I resized the canvas of the decal to be 9198x1526 pixels (again, the width was automatically calculated by GIMP based on a height of 1526 and a constant aspect ratio).

Next, I added an alpha channel to the decal layer and performed a "Layer->Layer to Image Size".

I then performed the Polar Coordinates operation, using an offset angle of 180 and unchecking the Map From Top option.

Finally, I autocropped the layer (resulting in a layer that was 562x139px).

The resulting decal layer was copied to the tire image to verify that it fit.

If done properly, the decal layer should be able to be added to a letter-sized image and printed on a 300DPI printer.

Saul,
I d/l your file, tried to create a decal sheet of multiples, and tried to print out a sample sheet on regular paper, only to find that the actual decal has only a 'whitewall height' of roughly half of what the actual 'whitewall' tire is (?!). I then tried to 'scale up' your decal to the actual RC tire size, but the arc does not even fit. I then used the file trando found, which is closer to the actual decal used on the real racecar tires, and once again, attempted to use your steps, but not getting the results. I gave the right dimensions for the actual tire diameter, 'whitewall' height, but somehow not moving forward. Any ideas?
Thanks for your patience!
S

Sc00by5ting · **Joined:** Aug 12, 2014 **Posts:** 29

trandoductin wrote:

interesting,

found a michelin on the internet and enlarged the lettering larger like shown in the wheels picture.
[ Image ]
I tried using polar coordinates as described above.
here's my try.
[ Image ]
here's the logo before i pasted on the hubcab
[ Image ]

glad to have learned something new today (how to curve a banner using polar coordinates

)

trando,
tried your curved logo, had to rescale it for the actual RC tire once again, but also has wrong arc. Somehow, this will be something so simple I've overlooked, it will drive me crazy!
S

Sc00by5ting · **Joined:** Aug 12, 2014 **Posts:** 29

trando,
took my RC tire pic, rescaled it actual size (139mm), then took your decal, rescaled it, printed out a sample, got a tire that is 95.5mm in diameter (arrrgggghh!!!)
Could I be overlooking something in printing, 'cos there's not much I can change in 'advanced' mode (HP 932C deskjet)
Cheers!
S

saulgoode · **Posted:** Fri Aug 22, 2014 4:16 pm **(#24)**

Sc00by5ting wrote:

Saul,
I d/l your file, tried to create a decal sheet of multiples, and tried to print out a sample sheet on regular paper, only to find that the actual decal has only a 'whitewall height' of roughly half of what the actual 'whitewall' tire is (?!).

Perhaps your printer is set to 600DPI? If so, see if there is way you can set it to print at 300DPI and print a test.

If that is the problem then repeat the steps in my preceding post but first scale the tire to be 139mm at 600DPI (before taking the other measurements).

Sc00by5ting · **Joined:** Aug 12, 2014 **Posts:** 29

Saul,
my printer is a 15yr-old printer, which can only max out @ 300dpi. I honestly don't know where the 'shift' of scale is happening, but it is. When I printed out my decals (from my other post), I had a 'magical' ratio of 1.05 with regards to what I had on the screen, to what I was printing out, both on my printer and my wife's 2yr-old printer. I'm at wit's end with this, because I'm not a graphical designer, so my field of knowledge is mm, not px, I'm used to a digital caliper, not a digital tablet. I really want to get these dcals done for my RC car. I'm going to step away from this this weekend, fix my motorcycle, start prepping my RC car for decals/paint, and will come back fresh, otherwise will just be frustrated from smacking my face against the wall with this.
Thanks for all your help guys!
S

Akros · **Joined:** Jan 10, 2013 **Posts:** 863

Sc00by5ting wrote:

I'm at wit's end with this, because I'm not a graphical designer, so my field of knowledge is mm, not px,

Sc00by5ting,
Perhaps this recent topic can bring you some new information.

"All that PPI does is affect the print size of the image. There are 2 ways that you can change the print size, (...)" - Wallace
The difference between DPI and PPI