Simple mod that can render blocks and items on-demand with a keybind (default `).
Hover over the item and press the key to render it and save it to a file. Hold CTRL while pressing the render key to open a GUI that lets you enter a comma-separated list of mod ids to render.
This mod will try to render the item as 512x512, but if your game window is too small it'll be limited to the width or height (whichever is smaller). This means you will get 480x480 renders with the default window size. Holding Shift while pressing the render key will render it at "actual size", whatever this means on your GUI scale. With the Normal GUI scale, this is 32x32.
This mod is available in my personal Maven repo, to make it easier to use in a dev env. Merge this with your build.gradle:
name = 'unascribed'
url = 'http://unascribed.com/maven/releases'
The old version 0.1 (for 1.7.10 only) will render every block and item in the game after the game finishes loading, excluding certain special blocks, and has a number of glitches. Use 0.3.