Difference between revisions of "Video modes"
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The standard [[video modes]] or '''Screen Modes'''. | The standard [[video modes]] or '''Screen Modes'''. | ||
| − | As a Colour | + | As a Colour Personal Computer, perhaps the Amstrad CPC best argument (beside being cheap, fully equipped and well rounded) was it's video capability. Yet this was also more demanding for the Z80 to handle compared to other lighter players such as ZX Spectrum. |
| − | Also Amstrad's Video RAM was shared | + | Also Amstrad's Video RAM was shared with the Z80 RAM. This and a cheap concept with fewer custom chips to ease the CPU could turn it into a sluggish snail if badly programmed. |
| − | Yet | + | Yet colourful games with few scrolling requirements, reflection games such as KLAX... were perhaps the easiest medium for a CPC to shine above other 8 bit computers. |
| − | Too bad too few | + | Too bad too few graphically-heavy Role-Playing Games were produced. |
==Specifications== | ==Specifications== | ||
| − | + | These are : | |
*'''Mode 0''': '''160×200''' pixels with 16 colors (4 bpp) | *'''Mode 0''': '''160×200''' pixels with 16 colors (4 bpp) | ||
| Line 22: | Line 22: | ||
The Video modes are known to display pixels with different sizes. | The Video modes are known to display pixels with different sizes. | ||
| − | Basically, the Amstrad CPC Video | + | Basically, the Amstrad CPC Video works like a CGA video card from a PC. But extra features like a 16 colours mode exist. |
The dimensions in pixels given could be raised with clever use of FullScreen Mode. | The dimensions in pixels given could be raised with clever use of FullScreen Mode. | ||
| Line 31: | Line 31: | ||
* Full screen'''Mode 2''': '''768x272''' pixels with 2 colors (1 bpp) | * Full screen'''Mode 2''': '''768x272''' pixels with 2 colors (1 bpp) | ||
| − | Also the use of | + | Also the use of scanline may increase vertical resolution. |
| − | == | + | ==Colour attributes== |
| − | The Amstrad CPC is perhaps the only cheap | + | The Amstrad CPC is perhaps the only cheap personal computer of this generation with absolutely no such thing as character colour attributes. |
| − | Speccy was | + | Speccy was awful for this, and even better computers had modes with it. |
| − | Later Thomson 8 bit computers (MO6 and TO8) used to have the same Video Modes and Palette as the Amstrad Plus and an additional Mode (320x200 and 16 colors with attribute limitation | + | Later Thomson 8 bit computers (MO6 and TO8) used to have the same Video Modes and Palette as the Amstrad Plus and an additional Mode (320x200 and 16 colors with attribute limitation of 4096 colours palette) |
| − | C64 and MSX also had | + | C64 and MSX also had Colour attributes, yet also some modes without or with less limitations than Speccy, and later models (C128, MSX2+ and 3) were also designed with even better extra non-attributed modes. |
| − | As a result, an Amstrad never | + | As a result, an Amstrad never sees any faulty colour clashes... despite the numerous speccy ports, because it cannot unless voluntarily programmed.... This saved many speccy ports indeed. |
Is this better ? | Is this better ? | ||
| − | Well colours attribute system allow a good resolution with more than 4 colours displayed on screen with | + | Well colours attribute system allow a good resolution with more than 4 colours displayed on screen with little effort. |
| − | So this would be interesting to display... | + | So this would be interesting to display...colourful texts. |
| − | Yet fine graphics with a really | + | Yet fine graphics with a really colourful feeling become harder to get, so are nice metallic or graphical effect letter fonts with 4 colors... |
==Colours== | ==Colours== | ||
| Line 73: | Line 73: | ||
The 3-level (not '''bits''') RGB uses three level for every red, green and blue color components, resulting in a 3<sup>3</sup> = 27 colours palette. | The 3-level (not '''bits''') RGB uses three level for every red, green and blue color components, resulting in a 3<sup>3</sup> = 27 colours palette. | ||
| − | A | + | A notable specification of the Amstrad CPC palette is that it offers only one "Grey". |
Compared to the C64 with...er...only greys..? (Humor inside) | Compared to the C64 with...er...only greys..? (Humor inside) | ||
| Line 79: | Line 79: | ||
This explains why in some games rocks and stone are coloured in other shades to get a good colour layer with more than 3 shades (black, grey and white). | This explains why in some games rocks and stone are coloured in other shades to get a good colour layer with more than 3 shades (black, grey and white). | ||
| − | * | + | *Examples : [[Defender of the Crown]] with Purple rocks and stone walls... Also [[Barbarian]]. |
It is also notable that this palette has a "lot" of Blue and Green variations... It is possible to use a mode 0 screen with almost only 16 pseudo Green and Blue colours (yet a bit purple for some of them). | It is also notable that this palette has a "lot" of Blue and Green variations... It is possible to use a mode 0 screen with almost only 16 pseudo Green and Blue colours (yet a bit purple for some of them). | ||
| − | Many | + | Many graphic programmers used mostly coloured flashy bold colours as it was often reproached by other 8bit fans (C64...). |
But a clever choice in said colours could also give good results too in Pastel shades. | But a clever choice in said colours could also give good results too in Pastel shades. | ||
| Line 116: | Line 116: | ||
http://upload.wikimedia.org/wikipedia/commons/3/3b/Screen_color_test_AmstradCPC_16colors.png | http://upload.wikimedia.org/wikipedia/commons/3/3b/Screen_color_test_AmstradCPC_16colors.png | ||
| − | Courtesy | + | Courtesy of Wikipedia. |
| − | Yet the | + | Yet the high amount of colours allows the use of Anti-Aliasing techniques to soften the shapes. |
| − | It is the mode that made CPC a '''Colour''' | + | It is the mode that made CPC a '''Colour''' Personal computer. |
| − | + | Dithering is sometimes used in this mode, yet the high number of colours allows better colour layers. | |
Dithering more offers a good "texture" or feel effect than real "new colours". | Dithering more offers a good "texture" or feel effect than real "new colours". | ||
| Line 128: | Line 128: | ||
==Mode 1 graphics== | ==Mode 1 graphics== | ||
| − | The pixels are square, but the only 4 colours | + | The pixels are square, but the only 4 colours per bit... few. |
http://upload.wikimedia.org/wikipedia/commons/3/3b/Screen_color_test_AmstradCPC_4colors.png | http://upload.wikimedia.org/wikipedia/commons/3/3b/Screen_color_test_AmstradCPC_4colors.png | ||
| − | Courtesy | + | Courtesy of Wikipedia. |
| − | Yet a massive amount of horizontal "split rasters" allows to multiply the number of colours displayed on the screen. | + | Yet a massive amount of horizontal "split rasters" allows you to multiply the number of colours displayed on the screen. |
| − | It's like using the colour attribute | + | It's like using the colour attribute specification (as on [[ZX Spectrum]]) but with horizontal limitations. |
Basically a CGA standard PC video display. | Basically a CGA standard PC video display. | ||
| − | Pictures and graphic material have to make good use of [[Dithering| | + | Pictures and graphic material have to make good use of [[Dithering|dithering]] in order to get a realistic look, yet the square pixels allow smooth dithering. |
==Mode 2 graphics== | ==Mode 2 graphics== | ||
| − | The pixels are 1x2, | + | The pixels are 1x2, extremely slim. |
http://upload.wikimedia.org/wikipedia/commons/4/48/Screen_color_test_AmstradCPC_2colors.png | http://upload.wikimedia.org/wikipedia/commons/4/48/Screen_color_test_AmstradCPC_2colors.png | ||
| − | Courtesy | + | Courtesy of Wikipedia. |
This mode is difficult to use in a coloured way. | This mode is difficult to use in a coloured way. | ||
| − | Better used as a Text Mode, yet it can be included in a | + | Better used as a Text Mode, yet it can be included in a split screen (games). |
Because of this Mode, the Amstrad CPC was perhaps one of the 8 bit computer able to display the highest screen resolution in Full Screen (the so called "overscan")... | Because of this Mode, the Amstrad CPC was perhaps one of the 8 bit computer able to display the highest screen resolution in Full Screen (the so called "overscan")... | ||
| Line 158: | Line 158: | ||
==Border== | ==Border== | ||
| − | The border allows 1 | + | The border allows 1 additional colour to be displayed on the screen with no tricks. |
==Amstrad Plus== | ==Amstrad Plus== | ||
| Line 166: | Line 166: | ||
This means 32 colours per screen with no tricks (including Border). | This means 32 colours per screen with no tricks (including Border). | ||
| − | Also it is worth noting that the resolution of | + | Also it is worth noting that the resolution of these Sprites (16x16 pixels) can be displayed through "magnification". |
The basic x1/x1 pixel is like a Mode2 Pixel (a x=1 and y=2 ratio...or X= 0.5 and Y=1). | The basic x1/x1 pixel is like a Mode2 Pixel (a x=1 and y=2 ratio...or X= 0.5 and Y=1). | ||
| Line 183: | Line 183: | ||
==External Links== | ==External Links== | ||
| − | [http://www.en.wikipedia.org/wiki/List_of_8-bit_computer_hardware_palettes Wikipedia's | + | [http://www.en.wikipedia.org/wiki/List_of_8-bit_computer_hardware_palettes Wikipedia's page on the different 8 Bit systems Hardware Palettes and Modes] including amstrad CPC of course... |
[http://en.wikipedia.org/wiki/List_of_monochrome_and_RGB_palettes#18-bit_RGB Wikipedia's page on RGB palette] including Amstrad CPC specific one | [http://en.wikipedia.org/wiki/List_of_monochrome_and_RGB_palettes#18-bit_RGB Wikipedia's page on RGB palette] including Amstrad CPC specific one | ||
| − | [http://sylvestre.grimware.org/cpc/ Les Sucres en Morceaux] the French site from supersly, shows many | + | [http://sylvestre.grimware.org/cpc/ Les Sucres en Morceaux] the French site from supersly, shows many examples and techniques to use the different Video mode of the amstrad CPC. |
[[Category:Graphic]][[Category:Programming]] | [[Category:Graphic]][[Category:Programming]] | ||
Revision as of 15:34, 24 October 2009
Contains stuff from Wikipedia.
The standard video modes or Screen Modes.
As a Colour Personal Computer, perhaps the Amstrad CPC best argument (beside being cheap, fully equipped and well rounded) was it's video capability. Yet this was also more demanding for the Z80 to handle compared to other lighter players such as ZX Spectrum.
Also Amstrad's Video RAM was shared with the Z80 RAM. This and a cheap concept with fewer custom chips to ease the CPU could turn it into a sluggish snail if badly programmed.
Yet colourful games with few scrolling requirements, reflection games such as KLAX... were perhaps the easiest medium for a CPC to shine above other 8 bit computers.
Too bad too few graphically-heavy Role-Playing Games were produced.
Contents
Specifications
These are :
- Mode 0: 160×200 pixels with 16 colors (4 bpp)
- Mode 1: 320×200 pixels with 4 colors (2 bpp)
- Mode 2: 640×200 pixels with 2 colors (1 bpp)
- Mode 3: 160x200 pixels with 4 colors (2bpp) (this is not an official mode, but rather a side-effect of the hardware)
The Video modes are known to display pixels with different sizes.
Basically, the Amstrad CPC Video works like a CGA video card from a PC. But extra features like a 16 colours mode exist.
The dimensions in pixels given could be raised with clever use of FullScreen Mode.
This then allows with a video memory of 24Ko (approximately) to displays on the standard screen up to :
- Full screen Mode 0: 192x272 pixels with 16 colors (4 bpp)
- Full screenMode 1: 384x272 pixels with 4 colors (2 bpp)
- Full screenMode 2: 768x272 pixels with 2 colors (1 bpp)
Also the use of scanline may increase vertical resolution.
Colour attributes
The Amstrad CPC is perhaps the only cheap personal computer of this generation with absolutely no such thing as character colour attributes.
Speccy was awful for this, and even better computers had modes with it.
Later Thomson 8 bit computers (MO6 and TO8) used to have the same Video Modes and Palette as the Amstrad Plus and an additional Mode (320x200 and 16 colors with attribute limitation of 4096 colours palette)
C64 and MSX also had Colour attributes, yet also some modes without or with less limitations than Speccy, and later models (C128, MSX2+ and 3) were also designed with even better extra non-attributed modes.
As a result, an Amstrad never sees any faulty colour clashes... despite the numerous speccy ports, because it cannot unless voluntarily programmed.... This saved many speccy ports indeed.
Is this better ? Well colours attribute system allow a good resolution with more than 4 colours displayed on screen with little effort.
So this would be interesting to display...colourful texts.
Yet fine graphics with a really colourful feeling become harder to get, so are nice metallic or graphical effect letter fonts with 4 colors...
Colours
- 3-level RGB
The Amstrad CPC (old) palette features 27 colours, despite the fact that the Video system (Gate Array and CRTC) could actually handle 32 colours.
Because this is a 3-level RGB custom palette.
This palette is used by the Amstrad CPC old series only and is not found in any other computers (but clones of course).
The 3-level (not bits) RGB uses three level for every red, green and blue color components, resulting in a 33 = 27 colours palette.
A notable specification of the Amstrad CPC palette is that it offers only one "Grey".
Compared to the C64 with...er...only greys..? (Humor inside)
This explains why in some games rocks and stone are coloured in other shades to get a good colour layer with more than 3 shades (black, grey and white).
- Examples : Defender of the Crown with Purple rocks and stone walls... Also Barbarian.
It is also notable that this palette has a "lot" of Blue and Green variations... It is possible to use a mode 0 screen with almost only 16 pseudo Green and Blue colours (yet a bit purple for some of them).
Many graphic programmers used mostly coloured flashy bold colours as it was often reproached by other 8bit fans (C64...).
But a clever choice in said colours could also give good results too in Pastel shades.
Yet Amstrad CPC had clearly a better palette (in number) than Speccy, C64, or almost all post-1985 8 bit computers.
It was a bit of a shame that some of its colours were almost identical...
- 12-bit RGB
Used by the Amstrad Plus series.
It's like the good old Amiga 500 palette.
Systems with a 12-bit RGB palette use 4 bits (16 values) for each of the red, green, and blue color components. This results in a 163 = 4096 colours palette. From the 8 bit era, only the latter MSX specs had a greater palette (in number).
Mode 0 graphics
Mode 0 graphics are blockier thanks to the "2x1" ratio.
Courtesy of Wikipedia.
Yet the high amount of colours allows the use of Anti-Aliasing techniques to soften the shapes.
It is the mode that made CPC a Colour Personal computer.
Dithering is sometimes used in this mode, yet the high number of colours allows better colour layers.
Dithering more offers a good "texture" or feel effect than real "new colours".
Mode 1 graphics
The pixels are square, but the only 4 colours per bit... few.
Courtesy of Wikipedia.
Yet a massive amount of horizontal "split rasters" allows you to multiply the number of colours displayed on the screen.
It's like using the colour attribute specification (as on ZX Spectrum) but with horizontal limitations.
Basically a CGA standard PC video display.
Pictures and graphic material have to make good use of dithering in order to get a realistic look, yet the square pixels allow smooth dithering.
Mode 2 graphics
The pixels are 1x2, extremely slim.
Courtesy of Wikipedia.
This mode is difficult to use in a coloured way.
Better used as a Text Mode, yet it can be included in a split screen (games).
Because of this Mode, the Amstrad CPC was perhaps one of the 8 bit computer able to display the highest screen resolution in Full Screen (the so called "overscan")...
You have to dither a lot to get a good picture as there are no real colours shades.
Border
The border allows 1 additional colour to be displayed on the screen with no tricks.
Amstrad Plus
The Amstrad Plus display the same modes, but 15 more colours can naturally be displayed thanks to the Hardwired Sprites.
This means 32 colours per screen with no tricks (including Border).
Also it is worth noting that the resolution of these Sprites (16x16 pixels) can be displayed through "magnification".
The basic x1/x1 pixel is like a Mode2 Pixel (a x=1 and y=2 ratio...or X= 0.5 and Y=1).
This can be multiplied by x2 or x4 in both dimensions (X and Y).
A mode 1 like pixel must then be a x2/x1 pixel. A mode 0 like pixel x4/x1.
Related pages
External Links
Wikipedia's page on the different 8 Bit systems Hardware Palettes and Modes including amstrad CPC of course...
Wikipedia's page on RGB palette including Amstrad CPC specific one
Les Sucres en Morceaux the French site from supersly, shows many examples and techniques to use the different Video mode of the amstrad CPC.
