: Make sunspot into Christmas tree I am working on a solar themed Christmas card and for that to work I need a Christmas tree shaped sunspot. I have tried to draw one by hand but I can't

@Sarah814

It can be done. The method shortly:


In Photoshop (or GIMP) rectify the edge of your sunspot to a linear row of those arcs. You can also make a syntethic version. (I will show both). We call the result "arc belt"
Goto Illustrator. Make "arc belt" pattern brush. Trace the arc belt raster image to vector and drag it to the brushes collection.
Draw with pen a tree. It must not have sharp corners nor other details which cannot have the arc belt stroke.
Apply the arc belt brush to the tree, add a black fill
Place under the tree the grainy sun surface texture. This can be done as well in Photoshop or Illustrator. Here a piece of sun was copied to Illustrator and used as a symbol.
Add the general Christmas card parts: decorations, text and frame.


Using rectified arc belt as stroke gave the following result:



The tree unfortunately cannot be much more complex because the amount of vector objects explodes and you will easily get error "Not enough memory" which halts the program. I also tried to add some decoration with narrower belt and making the belt locally narrower with the path width tool. It was quite far from a sunspot because the arc belt was replaced by something approaching to an ordinary stroke. But this is an artistic problem and beyond the question, which was technical.

How to do it:

At first your image needed some contrast enhancement (curves) and sharpening (unsharp mask). Obviously you have much better quality images than these screenshots. Black is good to be as deep as possible.

Rectifying the arc belt was done with filter Distort > Polar coordinates > Polar to rectilinear. The round sunspot was warped to more circular and placed to the center of the image (=exact square). I added a temporary symmetric pattern for aiming as a separate layer:



The white gaps due the warping do not harm because this layer is a duplicate. Applying the polar to rectilinear transform gave a straight belt. It got more sharpening. I used the the lens blur compensation in Filter > Sharpen > Smart Sharpen:



The next step was to posterize the image to 32 colors to have an idea how it will look out after tracing to vector. It also simplifies te deletion of unwanted parts.

The black area above the top edge was deleted (actually unnecessary)and some stray spots were erased. The bottom edge was cutted coarsely with the eraser. It was not exact, the idea was to remove the yellow sun and retain some of the hairiness of the belt. The result was copied & pasted to Illustrator and traced to 32 colors:



The piece of the belt was zoomed to smaller size and dragged to the Brushes collection. A vertically flipped copy was also made because I wasn't sure of the direction of the paths which will get it. The arcs look better, if their original black ends are on black in the final image.

The brush settings:



Remove the traced brush shape after creating the brush. It's too easy to accidentally apply the brush to the shape. It has thousands of paths => your machine will be freezed straight away.

A very simple tree was drawn. It got black fill and the arc belt brush stroke.There's no decoration (candles, stars, etc...) because the thickness of the arc belt does not allow complex shapes. There's as few anchor points as possible and only smooth ones. Sharp anchors make the belt overlap itself or leave gaps depending on the brush settings.

The grainy surface of the sun was taken from your image. A piece was selected with the direct selection tool to get highly irregular edges along grain borders.



It was traced to 16 colors in Illustrator and inserted to Symbols collection. The symbol was dragged to the artboard quite many times. To avoid apparent repeating it was used as flipped, rotated and slightly resized.

To stay beyond all scientific realism, the things can be also reversed. This version probably stands some ordinary decoration because there's black background. A black rectangle has got a hole in the pathfinder panel (minus).



The synthetic arc belt: It was obvious and quite soon proved too, that from the photo derived arc belt is extremely heavy load for my low resource system. I tried to make a synthetic version in Illustrator. In the following image the sun surface is a traced square taken from your photo, but the arc belt is synthetic:



1 and 2. A couple of differently colored arcs were drawn. Both have 2 different gradients placed onto a solid colored bar. Blending modes multiply and hard light are used.


Plenty of arcs were tiled to get a piece of belt. I planned to make the tiling with the pattern brush to get easily some random deviation, but it didn't accept gradients, not even as expanded. It was caused by the automatic clipping masks of the round ends. Removing them spoiled the apparent form. Manual tiling is tiresome. I rasterized and traced the arcs to 32 colors. After tracing and expanding the pattern brush worked ok and I got the arc tiling done fast.
The color wasn't ok due the wrong guesses in making arcs 1 - 2. I copied the piece of belt (3) to Photoshop and adjusted the color apparently to same as in the photo. The (again rasterized) piece of belt was used as pattern brush just like the rectified original belt.
A square taken from the photo, traced and used as a swatch for the background. The repeating of the same square is apparent. That was corrected in the version that used rectified original belt.


My judgement: The synthetic arc belt can look out too clean and finally it wasn't at all lighter load for the computer.

This is not tested, but the whole job could be easier in Photoshop. The arc belt could be painted with the pattern stamp. Several versions are needed for different directions and the tight corners must be crafted with special care.

Why easier? The result wouldn't kick the computer on its knees like the multi thousand shape Illustrator version.

Affinity designer: A PNG image with transparent background can be used just like a pattern brush in Illustrator. It bends very nicely along a path. There's no need to vectorize the image before using it as a brush. The only problem: The brushed stroke is a bitmap and like all bitmaps, it loses sharpness if enlargened.

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