Twain meets twain Use Spectrum screen pictures on your Amstrad with this program by J Keneally Creating screen pictures can be very time-consuming even with a good graphics designer. This program allows any Spectrum screen dump to be read into the Amstrad and developed onto the screen in the same colours. There are a wealth of excellent Spectrum screen pictures around which can be used as a starting point for your own Amstrad screens. Alternatively the program can be used to speed up title screen loading. Even on fast load, the 16K Amstrad screen takes along time to load. It is much quicker to create the screen on a Spectrum, dump it, and use that instead. It also makes life more difficult for the pirates!
To transfer between the Spectrum and CPC464 screens we must scan through each Spectrum screen pixel, then for each pixel check whether it is on or off, and decode the corresponding colour from the Attribute block. Now encode the colour into CPC464 (Mode 0) format and write the encoded colour to the screen. The process is slightly complicated by the mis-match of the number of horizontal pixels per line. On the Spectrum there are 256, on the CPC464 (Mode 0) only 160. We must either compress three Spectrum pixels into two on the CPC464 (covering 240 pixels on the Spectrum and losing the other 16), or 'frame out' any 160 pixels on the Spectrum without compression. Both these options are available in the program. Of course, the Spectrum screen dump must be read into the CPC464 first. This is read into locations 32768 onwards, using a special reader routine. This routine will in fact read in any Spectrum memory dump. Typing in should be straightforward, though it is easy to make errors when entering the Data statements in Lines 670 onwards. For this reason, each of these lines has a checksum incorporated. If you make a mistake you will get an error message when the program is run.
After running the program, you will be asked to load the Spectrum screen dump, and press a key to start loading it. On completion, you will have a blank screen with the legend:- F, W, I or S shown. These are the command keys as follows:- - F display the Full compressed picture
- W display a Window of 160 pixels. You select the window by entering a horizontal offset. A zero value means start from the extreme left of the picture. The code for this has been written mainly in Basic so that you can more easily follow how it works. It therefore runs much slower than the more complicated code for the 'F' command, which is in machine-code.
- I = change the colour of a particular ink. This allows you to instantaneously alter the colour of all parts painted in that ink.
- S = Save the screen to tape.
Program Notes Variables - ldscreen = address of Spectrum dump loader
- attr = routine to decode Spectrum colours
- fullsc = routine to create compressed picture
- xcoord,ycoord = pixel coords for Spectrum
- amdad = Amstrad display address
- spdad = Spectrum screen address
- pixel%,pap%,xunk%, = pixel on/off, paper, and ink colours from Spectrum
Line No - 80-160 Initialisation
- 170 Load Spectrum dump
- 180-210 Set ink colours
- 220-269 Select command
- 270-320 Dump Amstrad screen
- 330-350 Change ink colour
- 360-370 Do compressed picture
- 380-490 Do 'framed'picture
- 500-660 Routine to create machiner-code routines 670-840 Code for Spectrum dump loader
- 850-1100 Code for transfers.
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Page créée en 172 millisecondes et consultée 1951 foisL'Amstrad CPC est une machine 8 bits à base d'un Z80 à 4MHz. Le premier de la gamme fut le CPC 464 en 1984, équipé d'un lecteur de cassettes intégré il se plaçait en concurrent du Commodore C64 beaucoup plus compliqué à utiliser et plus cher. Ce fut un réel succès et sorti cette même années le CPC 664 équipé d'un lecteur de disquettes trois pouces intégré. Sa vie fut de courte durée puisqu'en 1985 il fut remplacé par le CPC 6128 qui était plus compact, plus soigné et surtout qui avait 128Ko de RAM au lieu de 64Ko. |
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