UTILITY -> Graphics
© _Shareware_ (1997)
Gifcon Version 4

Last Update : Tuesday 17 March 2015 at 23 h 36

Manual n° 1

_ // _______ _" _______ _______ _______ _ _ _ /______/ // /______/ /______/ /_____ / / I // // _ // // //__ // // // // I // //__//_ // ____ // /___/ // // // // II // /___ __/ // /__ / // // // // // // II // // //____// // // //_____ //____// // I / // /______/ // // /______/ /______/ // I_/ // " " " " " " " GIFCON version 4 SIOU This program allows to view GIF files on your favorite CPC computer. You can also save the screens in .SCR and .PAL formats compatible with OCP ART STUDIO file formats. The program requires the CPC full memory capacity and runs only on CPC 6128, as it uses the 128 Ko. Loading and running the program will erase any data up to &A600 in central memory and all the 2nd bank. External interfaces such as RAMCARD, ROMCARD, HACKER may cause unpredictable bugs especially when dealing with disk operations. ________________________________ This program is SHAREWARE ! You have been given kindly this program by me or a friend. If you got the SHAREWARE version, please register to receive the full version. If you have the complete software and use it, please register by sending me -------->>>> 30 FF to encourage my work ! <<<<-------- Upgraded versions will be available at low cost for registered people. ________________________________ - Here follow the main features of the version 4: * Choice of the CPC mode display. * Monochrome display. * Dithering options. * Color correction. * Interactive menu. * Rapid print included. * 80 Ko memory space for the conversion process. * 2 color GIF decoding. ________________________________ - Version 4 detailed characteristics: * Mode Display. You can convert the GIF picture to display it in the CPC mode 0, 1 or 2. Different combinations with dithering and viewing methods will produce special effects as described later. * Monochrome display. The palette is filled with the same color at increasing luminance values. Each color of the original GIF file is converted in the closest corresponding monochrome value. * Color correction. An optimisation of the color conversion is made by requiring a second pass of the GIF file. * Dithering effect. Two effects are available: Normal and Floyd Steinberg type. Where both options will slow down the conversion rate, normal dithering is a good compromise between image quality and conversion rate. * Interactive menu. The choice of the desired option is performed by moving the bright bar with arrow keys and by pressing <space>. For the 2 viewing methods, a catalogue of the selected drive is displayed. You can then choose your file as described above or press the ESC key. If you press this last key, you will return to the menu, the bright selection line in the catalogue list will disappear but the list will remain on screen. The second method of choosing a particular option is to press on the related key. Ex: To change drive, just press 'D'. The bright bar will not move. For the two viewing options, please refer below. * Interlace line decoding. This particular format implies some limitation on CPC 6128. While the original horizontal size from the GIF file is unlimited, the version 4 only displays files with a maximum of 1600 lines. This limitation is valid for screen small displays only. * Information display on the original GIF file. * Choice on image size display if the original size is bigger than the screen capabilities. You can choose to view the full image (compressed) or different sizes up to the original GIF maximum size. * Rapid Print. This is a short RSX software I was given to enhance the CPC basic PRINT routine. I decided to include it to my program. The original name is TURBOPRT.BIN. It is implanted from #A000 to #A600. RSX initialisation entry is at 41000. BUT if you want to have extra memory space for your program, you can use the TURBOPRT memory area (for ROM reserved space for example). The only thing you have to do is to clear memory from #A000 to #A600 before the first call to #1000. GIFCON4 will detect TURBOPRT is not present and will not crash... * Special effet for Interlaced GIF images. * Here is some details of the GIFCON4 memory organization: Bank 0: #0170-#1000 : Basic free space #1000-#4000 : Main program. Entry address: #1000 #4000-#8000 : GIF decompression charstream index / Bank switching area #8000-#8600 :*Current GIF char #8600-#9000 :*Area used for Floyd Steinberg dithering only. #9000-#9800 : Current GIF color global map #9800-#A000 : Disk buffer #A000-#A600 :*TURBOPRT Bank 1: #0000-#FFFF :*GIF decompression main charstream Areas marked with * can be used partly or fully for another use provided you do not select the corresponding options in the menu. Areas always used (#8000- #8600 (bank 0) and #0000-#FFFF (bank 1)) are filled from the bottom so if the GIF file does not require too much memory, you may have some free space for your own programmation. ________________________________ All options may be selected by the bright bar with arrow keys or with short cuts (exception is made for V and W). - Menu option description: D: Drive selection for load/save operations. !! CAUTION may be observed using this option. !! This option assumes you have a 'modern' 3'1/2 or 5'1/4 PC drive connected. Therefore selecting B: will change disk parameters to allow fast disk operations. Test if your drive does meet the B: conditions. If not, there will be a read fail. If you are in this case (unlucky guy !), ask me. You can anyway use the program but: - You do not use drive B: - or you must switch your drive selector to A: (If you don't have it, it is time for you to upgrade your CPC configuration...) M: Mode selection. You can select display mode 0, 1 or 2. The next lines give the available options for each mode: : View 1 : View 2 : Normal Dit. : F.Steinberg Dit. : Netscape : ---------------------------------------------------------------------+ Mode 0 : * : * : - : - : * : ---------------------------------------------------------------------+ Mode 1 : * : M : * : M : * : ---------------------------------------------------------------------+ Mode 2 : M : M : M : M : * : ---------------------------------------------------------------------- (M) Possible. Monochrome display. (*) Possible. Color display. (-) Impossible E: Dithering option. You can choose between no dithering, normal and F.Steinberg dithering. If the GIF file has interlaced lines, the dithering will be performed but will be of no meaning for the Floyd Steinberg type (the CPC does not have enough memory for that !). The array below sums up the possibilities: Dithering Effect : Mode 0 : Mode 1 (4 colors) : Mode 2 (2 colors) ----------------------------------------------------------------------- Normal : Off : Color / Monochrome : Monochrome ----------------------------------------------------------------------- Floyd : : : Steinberg : Off : Monochrome : Monochrome ----------------------------------------------------------------------- In order to reserve a large memory area for GIF decoding, the F.Steinberg algorithm is not strictly respected in the implemented dithering method. Therefore, it may result a strange image especially in mode 2. This effect does not generally happen for a mode 1 conversion. C: Makes a color correction of the last converted image. Once you have read a GIF file either with View 1 or View 2, just selected this option to make the correction. During the first reading of the original GIF file, the program keeps track of each GIF original color asked to be converted. The correction acts like a second pass, making statistics on GIF colors really included in the image. This option generally increase the color realism. I: View the converted image. By pressing the 'copy' key, you may alter the colors for monochrome modes. The set colors will then be used to save the file palette. Any other key will exit and return to the main menu. S: Save the displayed image in .SCR and .PAL formats (conpatible with ART STUDIO, IFFCON and HIPER). The name will be the same as the original GIF file. Once the image is displayed, a message is printed to confirm the operation. Depending on the colors in the palette, this message might not be visible. Therefore, you must know that you have to press 'Y' to save or any other key to return to the main menu. Although the message is displayed OVER the image, it does not affect the saved SCR image file. ! The shareware version does not have the save option available. A message ! ! will be printed to encourage you to register. ! V: Load, decod and view a GIF file on selected disk. If you press 'V', input the file name WITHOUT the .GIF extension. If you choose this option with the bright bar, make the selection with arrow keys and press the <space> key. The color conversion uses the 1st method converting the maximum of the GIF original colors into the palette. Once the palette has been converted, some information is displayed. You must choose the size of the image to put on screen. The different available sizes are proposed depending on the selected CPC mode. If you choose a resolution higher than the screen size, the program will display the upper left part of the GIF picture only. The choice is made by pressing one of the figures corresponding to the size chosen. Pressing the <space> bar will automatically select the highest number option in order to view the entire image. The border becomes blue when the conversion is over. If you get another color, a problem occured and the conversion is aborted. You can abort the file conversion by pressing the <space> bar continuously. W: As V but uses the 2nd method for color conversion. Some colors are always put into the palette before filling it with the GIF converted colors. N: Netscape effect !!!! Do not be afraid... I have not implemented Netscape... not yet... This option has a visible action on interlace line formats only. It permits to view the picture in an increasing resolution. This option is a flip-flop. This option will produce a random display when used with the Floyd Steinberg dithering method. Q: Quit... You may resume by typing 'call &1000'. ESC: Same as Q: Quit. _________________________ GIFCON version 4 has a known bug ! Yes, it is true, I have seen it on one particular file (only one from about 50 GIF files tested). This bug may appear when you want to view a file which caracteristics are: GIF with interlaced lines More than 200 lines in original size Display with compression (small size choice number) It is not really a problem to fix the bug, BUT I do not have this kind of image. Actually, it is very rare to encounter such a file with a size compatible with AMSDOS disks. If you get this bug, send me the original source GIF file on a 720Ko DOS disk. _________________________ A special discussion about memory usage is necessary to understand the most common error message given when reading GIF files. A GIF conversion needs a relatively large memory space to put a table. This table might expand up to 4 Mo depending on the image content! Fortunately, most of the GIF I have encountered do not need more than 64 Ko. If the GIF file needs more, you will not be able to view it with this version. The process will stop as soon as the memory is filled allowing you to view the first lines. The memory full error message will generally occur when a large area of the same color is found in the GIF file. There will be no problem (or the error will happen later) if a few pixels with another color are included in the area. The program is therefore very sensitive to GIF files with a 2 entry palette (i.e.: Black and white or monochrome pictures). The table might increase its size very fastly and stop the conversion. If you have the opportunity to modify the original GIF file with a PC, it might be good to expand the palette entry up to 256 and avoid large uniform areas (by making a light dithering for example). _________________________ ....................................... ....................................... .. .. .. - GIFCON version 5 will include .. .. the following features: .. .. .. .. - Reverse conversion : .. .. SCR (and PAL) to GIF 87a .. .. - Color Floyd Steinberg dithering .. .. - Increased memory space for .. .. 2 colors GIF file conversion .. .. - Compatibility with external .. .. ROMs such as ParaDOS or RODOS .. .. - Compatibility with my future .. .. ROM allowing direct 720 Ko DOS .. .. disk operations. .. .. .. .. - Remember to give me funds... .. .. .. ....................................... ....................................... _________________________ Contact: CNX SIOU MASSICOT LAURENT or MASSICOT LAURENT 23 RUE BOUQUIERES 37420 HUISMES 31000 TOULOUSE (FRANCE) (FRANCE) massicotàaltern.com http://www.geocities.com/CapeCanaveral/1044 CPC web page: ./CPC6128.html ***************************************************************************** *****************************************************************************

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