I opened an image from the internet in Illustrator.
Right after, when I selected the paintbrush tool, it turned into a circle with a line through it, implying that I couldn’t draw.
Does anyone know what happened and how I can fix this?
As others have said, Illustrator is not the right tool for editing “images from the internet” (which are normally raster).
However, I myself often use raster scans, typically JPG, as drafts for my vector illustrations. So I need to place vector on top of my raster image. And, like you said, when you open a raster image in Illustrator, the Brush tool is deactivated. I use the Pen tool 99% of the time and it works fine, so I haven’t noticed this issue until recently, when I went searching for solutions and found this post. I found some solution elsewhere so I’ll share it.
Don’t mind the artboard borders 🙂
The solution I found on TopBrushes went like this:
Go to the menu and select Window –> Brushes to open the little “Brushes” window. If it’s empty, you haven’t chosen a calligraphic style for your brush. Click on the arrow in the corner of the “Brushes” box, and select “Open brush library.” Pick a style, which will show up as a tab in the box, and your brush will work.
Here’s my result:
Notice that, in the Layers panel, when you drop down the image layer, you’ll see that your Brush-drawn object is now a separate sub-layer. This is very handy for those who work/trace on top of placed raster art: you lock the sub-layer with the raster (I prefer to move it to a separate bottom layer altogether), and you work with your vector brushes and pens and whatever in other layers. You can also turn your raster layer invisible easily to check how your vector is progressing.