PNG to B/W-TIF: Dither or nothing?

[Peter2]

I don't know - a bug or my fault:

I take a PNG and convert it with Batch-Prozessing to TIF (1 bit, B/W, LZW).
http://img412.imageshack.us/img412/8199/gedrehtlt0.png

When I use the setting "Dither", I get a dithered TIF, which I don't want.
http://img254.imageshack.us/img254/6113 ... herza9.png

When I use "no dither", I get an empty image.
http://img412.imageshack.us/img412/6572 ... hercs9.png

???

Peter

[rra]

Can't confirm this on xnview 194.2 :

dithering gives me the dithered B/W TIFF image,
selecting "no dither" gives me the non-dithered, yet halftoned pure black-white TIFF image, as should be !


René

[Drahken]

It seems to be an issue with the formula for setting it to binary. It turns solid white regardless whether you use the export function to export it to b/w tiff, png, gif, bmp, etc, or if you set it to b/w (without dither) directly in xnview. The problem is with the pale shade of the lines. If you set the lines to a darker color (this can be done by setting it to 16 colors & then editting the colormap to change the pale blue to a darker color, or by setting it to greyscale & then cranking the contrast up & darkness down) & THEN convert to binary, it'll come out as you would expect it to.

Also, if you just crank the contrast up on the original pic, it will turn white when you reach 86%.

[rra]

I would suspect that XNview does this (or should do this) already:
convert the image to grayscale, stretch the whole greyscale-image
between 0 and 255, and apply a threshold of value 128,
and making every pixel above 128 white (1)
and 128 and below equal to black (0) ??


René