HALFTONE PHOTOSHOP HELP please

Question

Bonjour,

Je vois sur Photoshop qu'il est possible de charger de nouvelles trames de demi teinte (format ahs) via le mode bitmap.

Très peu d'informations sur le web je ne sais pas comment créer un fichier ahs par moi même où via une conversion depuis png où jpg ?

Est ce que quelqu'un peut m'éclairer à ce sujet ?

Merci d'avance de vos réponses 🙂

🇺🇸🇬🇧

Hello,

I see in Photoshop that it is possible to load new halftone screens (ahs format) via bitmap mode. Very little information on the web I don't know how to create an ahs file by myself or via a conversion from png or jpg?

Can someone enlighten me on this?

Thank you in advance for your answers 🙂

Elise

Semaphoric · Accepted Answer

It seems like what you are looking for is PostScript Custom Spot Function. I found a rather old site that's still informative, Postscript Halftones - The Grymoire! but it doesn't say much about custom spots. He does recommend the book Real World Scanning and Halftones by David Blatner et al, which is out of print, but is excellent if you can find a copy.

You may be able to find more information in the PostScript Language Reference Manual.

Semaphoric · Answer

You can find the forat of .ahs files here . The relevant prt:

Halftone Screens

Halftone Screens settings files are loaded and saved in Photoshop's Halftone Screens dialog (available from Edit > Print with Preview in Photoshop 7, or Page Setup or Print Options in previous versions).

*Halftone screen file types*
OS	Filetype/extension
Mac OS	8BHS
Windows	.AHS

*Halftone screens file format*
Length	Description
2	Version ( = 5)
4*18	Four screen descriptions. See See Halftone screen parameter structure.
Variable	For every screen that has a custom spot function, the PostScript function text is written here, one after the other, with no header information, in the same order as the screen settings. The size of each custom spot is the absolute value of its negative shape code.

*Halftone screen parameter structure*
Length	Description
4	Ink's screen frequency, in lines per inch. Binary fixed point value ;16 bits representing the integer and fractional parts from 1.0...999.999.
2	Units for the screen frequency. Lines per inch = 1; lines per centimeter = 2. Only affects display, not screen frequency.
4	Angle for screen. Binary fixed point value with 16 bits representing the integer and fractional parts from -180.0000 ... 180.0000, measured in degrees.
2	Code representing the shape of the halftone dots. 0 = Round; 1 = Ellipse; 2 = Line; 3 = Square; 4 = Cross; 6 = Diamond. Negative numbers represent custom shapes; the absolute value is the size in bytes of the custom spot function described in See Halftone screens file format.
4	= 0. Not currently used by Photoshop.
1	Boolean. 1 = Use accurate screens; 0 = Use other.
1	Boolean. 1 = Use printer's default screens; 0 = Use other.

You may want to ask in the Postscript Forum

Halftone Screens

Sign up

To post, reply, or follow discussions, please sign in with your Adobe ID.

Sign in to Adobe Community

To post, reply, or follow discussions, please sign in with your Adobe ID.