GIF Images - QB64 Wiki

GIF Images

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Animated GIF File Decoder

GIF files can be one frame or animated images made up of many frames that are displayed at a set frame rate. The following program allows you to view either kind of image or use them in a program. _LOADIMAGE can only return one frame of an animated image.

NOTE: Include the FILELIST$ (function) or create your own File INPUT routine!

'####################################################################################### '# Animated GIF decoder v1.0 # '# By Zom-B # '# # '# If you find a GIF file that doesn't decode right, then please give me the # '# file so I can improve the algorithm. I can be found on www.qb64.net/forum # '####################################################################################### DEFINT A-Z '$DYNAMIC DIM SHARED Dbg: Dbg = 0 DIM SHARED powerOf2&(11) FOR a = 0 TO 11: powerOf2&(a) = 2 ^ a: NEXT a TYPE GIFDATA file AS INTEGER sigver AS STRING * 6 width AS _UNSIGNED INTEGER height AS _UNSIGNED INTEGER bpp AS _UNSIGNED _BYTE sortFlag AS _BYTE ' Unused colorRes AS _UNSIGNED _BYTE colorTableFlag AS _BYTE bgColor AS _UNSIGNED _BYTE aspect AS SINGLE ' Unused numColors AS _UNSIGNED INTEGER palette AS STRING * 768 END TYPE TYPE FRAMEDATA addr AS LONG left AS _UNSIGNED INTEGER top AS _UNSIGNED INTEGER width AS _UNSIGNED INTEGER height AS _UNSIGNED INTEGER localColorTableFlag AS _BYTE interlacedFlag AS _BYTE sortFlag AS _BYTE ' Unused palBPP AS _UNSIGNED _BYTE minimumCodeSize AS _UNSIGNED _BYTE transparentFlag AS _BYTE 'GIF89a-specific (animation) values userInput AS _BYTE ' Unused disposalMethod AS _UNSIGNED _BYTE delay AS SINGLE transColor AS _UNSIGNED _BYTE END TYPE SCREEN _NEWIMAGE(640, 480, 32) ' Open gif file. This reads the headers and palette but not the image data. ' The array will be redimentioned to fit the exact number of frames in the file. DIM gifData AS GIFDATA, frameData(0 TO 0) AS FRAMEDATA filename$ = "mygif.gif" '<<<<<<<<<<<< Enter a file name here!!! IF LEN(filename$) = 0 THEN END openGif filename$, gifData, frameData() ' Loop away. frame = 0 DO ' Request a frame. If it has been requested before, it is re-used, ' otherwise it is read and decoded from the file. _PUTIMAGE (0, 0), getGifFrame&(gifData, frameData(), frame) _DELAY frameData(frame).delay frame = (frame + 1) MOD (UBOUND(framedata) + 1) LOOP UNTIL LEN(INKEY$) 'Close the file and free the allocated frames. codeGif gifData, frameData() END '######################################################################################## SUB openGif (filename$, gifData AS GIFDATA, frameData() AS FRAMEDATA) STATIC file = FREEFILE: gifData.file = file OPEN "B", gifData.file, filename$ GET file, , gifData.sigver GET file, , gifData.width GET file, , gifData.height GET file, , byte~%% gifData.bpp = (byte~%% AND 7) + 1 gifData.sortFlag = (byte~%% AND 8) > 0 gifData.colorRes = (byte~%% \ 16 AND 7) + 1 gifData.colorTableFlag = (byte~%% AND 128) > 0 gifData.numColors = 2 ^ gifData.bpp GET file, , gifData.bgColor GET file, , byte~%% IF byte~%% = 0 THEN gifData.aspect = 0 ELSE gifData.aspect = (byte~%% + 15) / 64 IF gifData.sigver <> "GIF87a" AND gifData.sigver <> "GIF89a" THEN _DEST 0: PRINT "Invalid version": END IF NOT gifData.colorTableFlag THEN _DEST 0: PRINT "No Color Table": END palette$ = SPACE$(3 * gifData.numColors) GET file, , palette$ gifData.palette = palette$ IF Dbg AND 1 THEN PRINT "sigver ="; gifData.sigver PRINT "width ="; gifData.width PRINT "height ="; gifData.height PRINT "bpp ="; gifData.bpp PRINT "sortFlag ="; gifData.sortFlag PRINT "colorRes ="; gifData.colorRes PRINT "colorTableFlag ="; gifData.colorTableFlag PRINT "bgColor ="; gifData.bgColor PRINT "aspect ="; gifData.aspect PRINT "numColors ="; gifData.numColors FOR i = 0 TO gifData.numColors - 1 PRINT USING "pal(###) = "; i; PRINT HEX$(_RGB32(ASC(gifData.palette, i * 3 + 1), ASC(gifData.palette, i * 3 + 2), ASC(gifData.palette, i * 3 + 3))) NEXT END IF DO GET file, , byte~%% IF Dbg AND 2 THEN PRINT "Chunk: "; HEX$(byte~%%) SELECT CASE byte~%% CASE &H2C ' Image Descriptor IF frame > UBOUND(frameData) THEN REDIM _PRESERVE frameData(0 TO frame * 2 - 1) AS FRAMEDATA END IF GET file, , frameData(frame).left GET file, , frameData(frame).top GET file, , frameData(frame).width GET file, , frameData(frame).height GET file, , byte~%% frameData(frame).localColorTableFlag = (byte~%% AND 128) > 0 frameData(frame).interlacedFlag = (byte~%% AND 64) > 0 frameData(frame).sortFlag = (byte~%% AND 32) > 0 frameData(frame).palBPP = (byte~%% AND 7) + 1 frameData(frame).addr = LOC(file) + 1 IF frameData(frame).localColorTableFlag THEN SEEK file, LOC(file) + 3 * 2 ^ frameData(frame).palBPP + 1 END IF GET file, , frameData(frame).minimumCodeSize IF Dbg AND 2 THEN PRINT "addr ="; HEX$(frameData(frame).addr - 1) PRINT "left ="; frameData(frame).left PRINT "top ="; frameData(frame).top PRINT "width ="; frameData(frame).width PRINT "height ="; frameData(frame).height PRINT "localColorTableFlag ="; frameData(frame).localColorTableFlag PRINT "interlacedFlag ="; frameData(frame).interlacedFlag PRINT "sortFlag ="; frameData(frame).sortFlag PRINT "palBPP ="; frameData(frame).palBPP PRINT "minimumCodeSize ="; frameData(frame).minimumCodeSize END IF IF localColors THEN _DEST 0: PRINT "Local color table": END IF frameData(frame).disposalMethod > 2 THEN PRINT "Unsupported disposalMethod: "; frameData(frame).disposalMethod: END skipBlocks file frame = frame + 1 CASE &H3B ' Trailer EXIT DO CASE &H21 ' Extension Introducer GET file, , byte~%% ' Extension Label IF Dbg AND 2 THEN PRINT "Extension Introducer: "; HEX$(byte~%%) SELECT CASE byte~%% CASE &HFF, &HFE ' Application Extension, Comment Extension skipBlocks file CASE &HF9 IF frame > UBOUND(frameData) THEN REDIM _PRESERVE frameData(0 TO frame * 2 - 1) AS FRAMEDATA END IF GET 1, , byte~%% ' Block Size (always 4) GET 1, , byte~%% frameData(frame).transparentFlag = (byte~%% AND 1) > 0 frameData(frame).userInput = (byte~%% AND 2) > 0 frameData(frame).disposalMethod = byte~%% \ 4 AND 7 GET 1, , delay~% IF delay~% = 0 THEN frameData(frame).delay = 0.1 ELSE frameData(frame).delay = delay~% / 100 GET 1, , frameData(frame).transColor IF Dbg AND 2 THEN PRINT "frame ="; frame PRINT "transparentFlag ="; frameData(frame).transparentFlag PRINT "userInput ="; frameData(frame).userInput PRINT "disposalMethod ="; frameData(frame).disposalMethod PRINT "delay ="; frameData(frame).delay PRINT "transColor ="; frameData(frame).transColor END IF skipBlocks file CASE ELSE PRINT "Unsupported extension Label: "; HEX$(byte~%%): END END SELECT CASE ELSE PRINT "Unsupported chunk: "; HEX$(byte~%%): END END SELECT LOOP REDIM _PRESERVE frameData(0 TO frame - 1) AS FRAMEDATA END FUNCTION SUB skipBlocks (file) DO GET file, , byte~%% ' Block Size IF Dbg AND 2 THEN PRINT "block size ="; byte~%% SEEK file, LOC(file) + byte~%% + 1 LOOP WHILE byte~%% END SUB FUNCTION getGifFrame& (gifData AS GIFDATA, frameData() AS FRAMEDATA, frame) IF frameData(frame).addr > 0 THEN IF Dbg AND 4 THEN PRINT "addr ="; HEX$(frameData(frame).addr - 1) PRINT "left ="; frameData(frame).left PRINT "top ="; frameData(frame).top PRINT "width ="; frameData(frame).width PRINT "height ="; frameData(frame).height PRINT "localColorTableFlag ="; frameData(frame).localColorTableFlag PRINT "interlacedFlag ="; frameData(frame).interlacedFlag PRINT "sortFlag ="; frameData(frame).sortFlag PRINT "palBPP ="; frameData(frame).palBPP PRINT "minimumCodeSize ="; frameData(frame).minimumCodeSize PRINT "transparentFlag ="; frameData(frame).transparentFlag PRINT "userInput ="; frameData(frame).userInput PRINT "disposalMethod ="; frameData(frame).disposalMethod PRINT "delay ="; frameData(frame).delay PRINT "transColor ="; frameData(frame).transColor END IF w = frameData(frame).width h = frameData(frame).height img& = _NEWIMAGE(w, h, 256) frame& = _NEWIMAGE(gifData.width, gifData.height, 256) _DEST img& decodeFrame gifData, frameData(frame) _DEST frame& IF frameData(frame).localColorTableFlag THEN _COPYPALETTE img& ELSE FOR i = 0 TO gifData.numColors - 1 _PALETTECOLOR i, _RGB32(ASC(gifData.palette, i * 3 + 1), ASC(gifData.palette, i * 3 + 2), ASC(gifData.palette, i * 3 + 3)) NEXT END IF IF frame THEN SELECT CASE frameData(frame - 1).disposalMethod CASE 0, 1 _PUTIMAGE , frameData(frame - 1).addr CASE 2 CLS , gifData.bgColor _CLEARCOLOR gifData.bgColor END SELECT ELSE CLS , gifData.bgColor END IF IF frameData(frame).transparentFlag THEN _CLEARCOLOR frameData(frame).transColor, img& END IF _PUTIMAGE (frameData(frame).left, frameData(frame).top), img& _FREEIMAGE img& frameData(frame).addr = frame& _DEST 0 END IF getGifFrame& = frameData(frame).addr END FUNCTION '############################################################################################ SUB decodeFrame (gifdata AS GIFDATA, framedata AS FRAMEDATA) DIM byte AS _UNSIGNED _BYTE DIM prefix(4095), suffix(4095), colorStack(4095) startCodeSize = gifdata.bpp + 1 clearCode = 2 ^ gifdata.bpp endCode = clearCode + 1 minCode = endCode + 1 startMaxCode = clearCode * 2 - 1 nvc = minCode codeSize = startCodeSize maxCode = startMaxCode IF framedata.interlacedFlag THEN interlacedPass = 0: interlacedStep = 8 bitPointer = 0 blockSize = 0 blockPointer = 0 x = 0 y = 0 file = gifdata.file SEEK file, framedata.addr IF framedata.localColorTableFlag THEN palette$ = SPACE$(3 * 2 ^ framedata.palBPP) GET 1, , palette$ FOR i = 0 TO gifdata.numColors - 1 c& = _RGB32(ASC(palette$, i * 3 + 1), ASC(palette$, i * 3 + 2), ASC(palette$, i * 3 + 3)) _PALETTECOLOR i, c& NEXT END IF GET file, , byte ' minimumCodeSize DO GOSUB GetCode stackPointer = 0 IF code = clearCode THEN 'Reset & Draw next color direct nvc = minCode ' \ codeSize = startCodeSize ' Preset default codes maxCode = startMaxCode ' / GOSUB GetCode currentCode = code lastColor = code colorStack(stackPointer) = lastColor stackPointer = 1 ELSEIF code <> endCode THEN 'Draw direct color or colors from suffix currentCode = code IF currentCode = nvc THEN 'Take last color too currentCode = oldCode colorStack(stackPointer) = lastColor stackPointer = stackPointer + 1 END IF WHILE currentCode >= minCode 'Extract colors from suffix colorStack(stackPointer) = suffix(currentCode) stackPointer = stackPointer + 1 currentCode = prefix(currentCode) 'Next color from suffix is described in WEND ' the prefix, else prefix is the last col. lastColor = currentCode ' Last color is equal to the colorStack(stackPointer) = lastColor ' last known code (direct, or from stackPointer = stackPointer + 1 ' Prefix) suffix(nvc) = lastColor 'Automatically, update suffix prefix(nvc) = oldCode 'Code from the session before (for extracting from suffix) nvc = nvc + 1 IF nvc > maxCode AND codeSize < 12 THEN codeSize = codeSize + 1 maxCode = maxCode * 2 + 1 END IF END IF FOR i = stackPointer - 1 TO 0 STEP -1 PSET (x, y), colorStack(i) x = x + 1 IF x = framedata.width THEN x = 0 IF framedata.interlacedFlag THEN y = y + interlacedStep IF y >= framedata.height THEN SELECT CASE interlacedPass CASE 0: interlacedPass = 1: y = 4 CASE 1: interlacedPass = 2: y = 2 CASE 2: interlacedPass = 3: y = 1 END SELECT interlacedStep = 2 * y END IF ELSE y = y + 1 END IF END IF NEXT oldCode = code LOOP UNTIL code = endCode GET file, , byte EXIT SUB GetCode: IF bitPointer = 0 THEN GOSUB ReadByteFromBlock: bitPointer = 8 WorkCode& = LastChar \ powerOf2&(8 - bitPointer) WHILE codeSize > bitPointer GOSUB ReadByteFromBlock WorkCode& = WorkCode& OR LastChar * powerOf2&(bitPointer) bitPointer = bitPointer + 8 WEND bitPointer = bitPointer - codeSize code = WorkCode& AND maxCode RETURN ReadByteFromBlock: IF blockPointer = blockSize THEN GET file, , byte: blockSize = byte a$ = SPACE$(blockSize): GET file, , a$ blockPointer = 0 END IF blockPointer = blockPointer + 1 LastChar = ASC(MID$(a$, blockPointer, 1)) RETURN END SUB SUB codeGif (gifData AS GIFDATA, frameData() AS FRAMEDATA) FOR i = 0 TO UBOUND(FRAMEDATA) IF frameData(i).addr < 0 THEN _FREEIMAGE frameData(i).addr NEXT CLOSE gifData.file END SUB

NOTE: If full code is not displayed then refresh browser.


Using with $INCLUDE: 'FILELIST$.BM' File
Copy the code from the FILELIST$ (function) or FILELIST$ page to a text file named _FILE$.BM and use when compiling. Just save with .BM extension (Save As ALL files) in Notepad or other text editor. The file is not necessary after the program is compiled.


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