RE: Which colors for a grayscale?
I have a lovely place for all my Z80 source, it's called a 3.5 disk box... must get it organized some time :-). In this case it is so short, here it is: ORG 6 DUMP $ JP start DEFM DEFM GREY-SCALE DITHERER DEFM DEFM This program changes all odd DEFM colour pixels to a stipple DEFM pattern of even colours. DEFM DEFM (C) 1993 Solar Flare of ENTROPY DEFM Completion date: 4 October 1993 DEFM Idea: Robert van der Veeke start: LD HL,32768 loop: LD B,128 line0: LD A,(HL) AND %11101110 CP (HL) JR Z,nochange LD A,(HL) AND %1110 LD C,A LD A,(HL) AND % CP C JR Z,leftsame LD A,(HL) AND %1110 LD C,A LD A,(HL) AND % CP C JR NZ,changeboth LD A,(HL) AND %11101110 LD (HL),A JR nochange leftsame: LD A,(HL) AND % LD C,A LD A,(HL) AND % INC A CP 14 JR C,$+4 LD A,%1110 OR C LD (HL),A JR nochange changeboth: LD A,(HL) AND %1110 LD C,A LD A,(HL) AND % INC A CP 14 JR C,$+4 LD A,14 OR C LD (HL),A nochange: LD A,(HL) RRCA LD (HL),A INC HL DJNZ line0 LD B,128 line1: LD A,(HL) AND %11101110 CP (HL) JR Z,nochange1 LD A,(HL) AND % LD C,A LD A,(HL) AND %1110 CP C JR Z,leftsame1 LD A,(HL) AND %1110 LD C,A LD A,(HL) AND % CP C JR NZ,changeboth1 LD A,(HL) AND %1110 LD C,A LD A,(HL) AND % ADD 16 JR NC,$+4 LD A,%1110 AND %1110 OR C LD (HL),A JR nochange1 leftsame1: LD A,(HL) AND %11101110 LD (HL),A JR nochange1 changeboth1: LD A,(HL) AND %1110 LD C,A LD A,(HL) AND % ADD A,16 JR NC,$+4 LD A,%1110 AND %1110 OR C LD (HL),A nochange1: LD A,(HL) RRCA LD (HL),A INC HL DJNZ line1 LD A,H CP 128+96 JP NZ,loop RET -Original Message- From: owner-sam-us...@nvg.ntnu.no [mailto:owner-sam-us...@nvg.ntnu.no] On Behalf Of Marcos Cruz Sent: dinsdag 25 december 2012 02:06 To: sam-users@nvg.ntnu.no Subject: Re: Which colors for a grayscale? En/Je/On 2012-12-20 05:00, Stefan Drissen escribió / skribis / wrote : I wrote the greyscale ditherer - see [1]http://www.worldofsam.org/node/40 Stefan, do you keep the Z80 source? If so, would you share it? I'd like to adapt your routine to work on any region of the current screen. I'd publish the modified version with the original credits and a link to its page on World of Sam. Probably changing some values will be enough, but I didn't try to disassemble it yet. Marcos -- http://programandala.net
Re: Which colors for a grayscale?
En/Je/On 2012-12-20 05:00, Stefan Drissen escribió / skribis / wrote : I wrote the greyscale ditherer - see [1]http://www.worldofsam.org/node/40 Stefan, do you keep the Z80 source? If so, would you share it? I'd like to adapt your routine to work on any region of the current screen. I'd publish the modified version with the original credits and a link to its page on World of Sam. Probably changing some values will be enough, but I didn't try to disassemble it yet. Marcos -- http://programandala.net
Re: Which colors for a grayscale?
En/Je/On 2012-12-20 05:00, Stefan Drissen escribió / skribis / wrote : I wrote the greyscale ditherer - see [1]http://www.worldofsam.org/node/40 - it only uses the real greys and dithers the in between a. Thank you Stefan. My first try sprite is 54x28, only few pixels got cyan using the colorscale suggested by Simon, and of course it's an alien spacesship on black background, so it looks nice with some cyanish touches :) But your code does an impresive job. I'll use it to create alternative gray-only sprites. Marcos -- http://programandala.net
Re: Which colors for a grayscale?
Hi Marcos, The SAM palette is make up using 2-bit RGB plus intensity, which bitwise is: xGRBigrb. For pure greys you'd use: = 00 = 0 0111 = 07 = 7 1000 = 08 = 8 = 0f = 15 0111 = 70 = 112 01110111 = 77 = 119 0000 = 78 = 120 0111 = 7f = 127 The SAM demo tape astronaut image uses cyan to fill some of the gaps, which duplicates black and white on the ends: 0, 0, 8, 5, 7, 13, 15, 82, 112, 90, 120, 117, 119, 125, 127, 127 That's maybe as good as you'll get for a 16-colour palette. Si On 19/12/2012 20:43, Marcos Cruz wrote: Hi all, In order to automate and simplify as much as possible the process of importing images into the SAM and avoid the palette conversion problems, I'm tinkering with the Netpbm raster formats (http://en.wikipedia.org/wiki/Netpbm_format). BMP and others could be used too, but Netpbm files have two encoding variants (ASCII and binary) for every type (PBM, PGM and PPM), what makes them very versatile in this case. The Netpbm images are created with Linux tools and the SAM does the final conversion, PLOTing the image pixels with the desired equivalent colors and GRABbing it. The first tries with a grayscale image look promising, but I need to choose 16 grays from the SAM palette (0, 7, 8, 15, 112, 120, 127...?) I'm afraid there are less than 16 gray tones, and blue must be used to complete the set. Am I right? Does anyboy know which are the best 16 SAM original colors for a grayscale? Thank you. Marcos
Re: Which colors for a grayscale?
En/Je/On 2012-12-19 21:54, Simon Owen escribió / skribis / wrote : bitwise is: xGRBigrb. For pure greys you'd use: = 00 = 0 0111 = 07 = 7 1000 = 08 = 8 = 0f = 15 0111 = 70 = 112 01110111 = 77 = 119 0000 = 78 = 120 0111 = 7f = 127 I already knew the format but didn't have the idea to confirm which colors are actually gray just by looking its code. I see my eyes worked fine anyway :) 0, 0, 8, 5, 7, 13, 15, 82, 112, 90, 120, 117, 119, 125, 127, 127 That's what I needed. It looks great. I'll try a 14-gray variant; the two duplicates can be useful for some color effect. Thank you. Marcos -- http://programandala.net
Re: Which colors for a grayscale?
Although the cyanish in between colours looked good on an old CRT television, I thought they looked horrible on a monitor. That's why I wrote the greyscale ditherer - see http://www.worldofsam.org/node/40 - it only uses the real greys and dithers the in between a. Op 19 dec. 2012 om 22:54 heeft Simon Owen simon.o...@simcoupe.org het volgende geschreven: Hi Marcos, The SAM palette is make up using 2-bit RGB plus intensity, which bitwise is: xGRBigrb. For pure greys you'd use: = 00 = 0 0111 = 07 = 7 1000 = 08 = 8 = 0f = 15 0111 = 70 = 112 01110111 = 77 = 119 0000 = 78 = 120 0111 = 7f = 127 The SAM demo tape astronaut image uses cyan to fill some of the gaps, which duplicates black and white on the ends: 0, 0, 8, 5, 7, 13, 15, 82, 112, 90, 120, 117, 119, 125, 127, 127 That's maybe as good as you'll get for a 16-colour palette. Si On 19/12/2012 20:43, Marcos Cruz wrote: Hi all, In order to automate and simplify as much as possible the process of importing images into the SAM and avoid the palette conversion problems, I'm tinkering with the Netpbm raster formats (http://en.wikipedia.org/wiki/Netpbm_format). BMP and others could be used too, but Netpbm files have two encoding variants (ASCII and binary) for every type (PBM, PGM and PPM), what makes them very versatile in this case. The Netpbm images are created with Linux tools and the SAM does the final conversion, PLOTing the image pixels with the desired equivalent colors and GRABbing it. The first tries with a grayscale image look promising, but I need to choose 16 grays from the SAM palette (0, 7, 8, 15, 112, 120, 127...?) I'm afraid there are less than 16 gray tones, and blue must be used to complete the set. Am I right? Does anyboy know which are the best 16 SAM original colors for a grayscale? Thank you. Marcos
