Quote:
Originally Posted by NiLuJe
my current rescale + letterbox + grayscale + dither pass of choice looks something like this:
Code:
convert input.png -colorspace Lab -filter LanczosSharp -distort Resize 1080x1429 -colorspace sRGB -background black -gravity center -extent 1080x1429! -grayscale Rec709Luminance -colorspace sRGB -dither Riemersma -remap eink_cmap.gif -quality 75 png:out.png
1080x1429 being the effective resolution of an H2O  .
With the cmap attached here. |
NiLuJe,
Can you please explain these options a bit more?
1) I tried dithering manga files produced by Kindle Comic Converter with Riemersma and Floyd-Steinberg dithering. I feel like Floyd-Steinberg produces slightly more grainy images overall, but the gradient look much smoother. Is it acceptable by Kindle?
2) Do I have to apply all these options if I only want to add dithering? For example, can I skip filtering? What's the difference between resize and extent? What is gravity?
3) Some of my input files are actually jpg. Should I still convert them to png? Is it bad if I save them as jpg?
4) Why are there two mentions of colorspace? First is Lab, another one is sRGB
5) I have a different one-liner to convert images (I think I found it when I was converting screensavers). It has "-define png:color-type=0 -define png:bit-depth=8". Should I apply these too?