Extract image width+height without loading - bb3d

-=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- (c) WidthPadding Industries 1987 0\|535\|0 -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=- -=+=-
SoCoder -> Snippet Home -> File Access

Dan	Created : 28 October 2018 Edited : 28 October 2018 System : Windows Language : Blitz Extract image width+height without loading - bb3d Reads image information from bmp/jpg/png/tga/gif without loading the file
; ; imageInfo.bb v1.1b ; (C)2003 Graham Plumb ; ; This function returns the width and height of an image, and places them into global ; variables called iiWidth and iiHeight, WITHOUT the need to load the image first and ; then use ImageHeight/ImageWidth commands. ; ; The point of this is purely for speed, as for large images the overhead of loading ; the image, just to get it's dimensions, is a bit excessive - for example when creating ; sprite textures. ; ; This function works on BMP, GIF, PNG, JPEG and TGA (2.0) images, in that order, but decides ; which type the image is by checking it's signature (the proper way of doing things) ; and NOT by the filename's extension. ; ; Provision for plugging in your own code (to support other formats) has been left in the ; code's logic. ; ; Feel free to use this code, all I ask is for some sort of acknowledgement in the program ; Global iiWidth Global iiHeight Function getImageInformation(filename$) Local han = OpenFile(filename$) iiWidth = 0 iiHeight = 0 recognised = 0 If (han) Then ; used to store the first 8 bytes of this file... (for signature checking ; to determine the file's type) ; ; An array was NOT used as this has to be global and there is no need for a global ; array of the first 8 bytes of a file! These variables are LOCAL by default and ; so will be removed at the end of the function call from memory ch_0 = 0: ch_1 = 0: ch_2 = 0: ch_3 = 0: ch_4 = 0: ch_5 = 0: ch_6 = 0: ch_7 = 0 ; read in the data... ch_0 = ReadByte(han) ch_1 = ReadByte(han) ch_2 = ReadByte(han) ch_3 = ReadByte(han) ch_4 = ReadByte(han) ch_5 = ReadByte(han) ch_6 = ReadByte(han) ch_7 = ReadByte(han) ; The signature for a bitmap... If ch_0=66 And ch_1=77 Then ; Print "BITMAP" ; go to useful info... SeekFile(han,18) iiWidth = ReadInt(han) iiHeight = ReadInt(han) recognised = 1 ; Print "Image is "+width+" * "+height Else ; The signature for a GIF... If ch_0=71 And ch_1=73 And ch_2=70 Then ; Print "GIF" SeekFile(han,6) ch_0 = ReadByte(han) ch_1 = ReadByte(han) ch_2 = ReadByte(han) ch_3 = ReadByte(han) iiWidth = ch_1 * 256 + ch_0 iiHeight = ch_3 * 256 + ch_2 recognised = 1 ; Print width+" * "+height Else ; The signature for a PNG... (YES - 8 byte's worth!!) If ch_0=137 And ch_1=80 And ch_2=78 And ch_3=71 And ch_4=13 And ch_5=10 And ch_6=26 And ch_7=10 Then ; Print "PNG" ; PNG actually implements CRC checking on all of its data chunks to see if ; they are valid (as PNGs are for net-work transportation and therefore prone ; to corruption) ; ; For the sake of speed I have not calculated the header's CRC and compared ; it to the value in the CRC field for that chunk SeekFile(han,18) iiWidth = ReadByte(han) * 256 + ReadByte(han) SeekFile(han,22) iiHeight = ReadByte(han) * 256 + ReadByte(han) recognised = 1 ; Print width+""+height Else ; The signature for a JPEG If ch_0=255 And ch_1=216 Then ; Print "JPEG" ; JPEG actually checks the 2 bytes at the beginning of the file and 2 bytes from the ; end to give FF D8 (at the start) and FF D9 (at the end) ; ; For the sake of speed, I have neglected the footer signature and use only the header ; to decide if the image is a JPEG. This is because we don't have to wait for the HDD ; heads to move to the end of the file (bar 2 bytes) - the seek time ;Dan 28.10.2018 - added a solution found on https://stackoverflow.com/questions/18264357/how-to-get-the-width-height-of-jpeg-file-without-using-library SeekFile (han,2) ;y=0 Repeat If Eof(han) Or recogised=1 Then Exit ;y=y+1 : If y=1500 Then Delay 5 : y=0 ;Don't freeze the prog if the file is extra large ... remove if not needed Marker=ReadByte(han) If marker=$ff marker1=ReadByte(han) If marker1=$c0 Or marker1=$c2 ReadByte(han):ReadByte(han):ReadByte(han) iiHeight = ReadByte(han) 256 + ReadByte(han) iiWidth = ReadByte(han) * 256 + ReadByte(han) recognised = 1 Else marker=marker1 EndIf EndIf Forever ; Print width+" * "+height Else ; Use this part of the logic to implement your own header-based signature ; file formats. Ensure that recognised is set to 1 after iiWidth and iiHeight ; has been set. Note, if your format is a footer-based signature (ie. you have ; to count x bytes from the end of the file) then use the branch of logic that ; follows to try and minimise seek times EndIf EndIf EndIf EndIf ; No header-signatures are found, now look for file types that use footer ; signatures - like TGA 2.0... If recognised = 0 Then ; Last 18 Bytes used for TGA - this size may need to be adjusted depending ; on the signatures of any types of footer-based signature formats you ; wish to code for SeekFile(han, Int(FileSize(filename$))-18) ext$=Lower$(Right$(filename$,3)) temp$ = "" For x = 1 To 17 temp$ = temp$ + Chr$(ReadByte(han)) Next If (temp$="TRUEVISION-XFILE." And ReadByte(han)=0) Or ext$="tga" Then ;dan added tga extension workaround, as some files do not contain the "truevision-xfile" signature ; Print "TGA (2.0)" SeekFile(han, 12) iiWidth = ReadByte(han) + ReadByte(han) * 256 iiHeight = ReadByte(han) + ReadByte(han) * 256 ; Print iiWidth+" * "+iiHeight recognised = 1 Else ; Other signature strings can be checked here... ; ; Note, the string gleaned from the above loop may need to be ; changed depending on the other footer-based signature formats ; that you plan to code here. EndIf EndIf ; Code not necessarily needed ; If recognised = 0 Then ; Print "Unknown file type" ; EndIf Else ; REMmarked out for ease of use (soft-error handling) ; ; Note that in debugMode, Blitz will throw up a dialog box! If (han = 0) Then ; Print "File not found." Else ; Print "Not enough data!" EndIf EndIf CloseFile(han) End Function ;* imageInfoTest * ; Include the imageInfo file to give us access to the getImageInformation function... ;Include "imageInfo.bb" ;Simple test: ;getImageInformation("c:\test.png") ;Print iiWidth+" x "+iiHeight ;waitkey() --v
Latest Update This sourcecode is not my own, i'v just added some fixes, so now it can read the jpg file size corectly (see the sourcecode for more info). Below is a demonstration program, but you need the acceptfiles.dll and optionally the user32.decls with the api_GetSystemMetrics% addition (see the below code for more info) The demo-program opens a window in which you can drag'n'drop image files. For each file height and width will be displayed. ;User32.decls: add next 2 lines, and save the text into "blitzbasic/userlibs/" folder. ;.lib "user32.dll" ;api_GetSystemMetrics% (nIndex%) : "GetSystemMetrics" DeskY=api_GetSystemMetrics(1)-62 ;Get the Desktop height and substract 62 from it. ;DeskY=800 Graphics 640,DeskY,32,2 Graphics 640,DeskY,32,3 ;acceptfiles.dll download from ChristianK here: https://www.blitzforum.de/forum/viewtopic.php?p=313456&highlight=#313456 InitAcceptFiles( SystemProperty( "AppHWND" ) ) AcceptFiles True ;aceptfiles.dll AppTitle "Drag'n'Drop image files here:" Repeat Local c = AcceptedFileCount( ) ;Process the files dropped (uses acceptfiles.dll) For i=0 To c-1 ;Drag'n'Drop support - acceptfiles.dll If i=0 Then Color $ff,$ff,$0 : Print CurrentTime$() : Color $ff,$ff,$ff AF$=AcceptedFile( i ) getImageInformation(AF$) a=InstrLast(AF$,"\") ext$=Lower$(Right$(Af$,3)) : ext1$=Lower$(Right$(Af$,4)) Select True Case iiHeight=0 And iiWidth=0 Color $ff,$0,$0 skip=1 Case ext$="jpg" Color $ff,$50,$90 Case ext1$="jpeg" Color $ff,0,0 Case ext$="gif" Color $50,$50,$ff Case ext$="png" Color $ff,$0,$ff Case ext$="tga" Color $0,$ff,$ff Case ext$="bmp" Color $50,$50,$50 Default Color $ff,$ff,$ff End Select If skip=0 Then Print RSet(iiWidth,7)+" x "+LSet(iiHeight, 7)+ " - "+Mid$(AF$,a+1,Len(AF$)-(a-1)) skip=0 Delay 5 Next Delay 5 Until KeyDown(1) End Function InstrLast(s$,c$) ;Returns the starting point of the last occurence of c$ startpos=1 lastpos=0 .repeat_instrlast a=Instr(s$,c$,startpos) If a>0 Then startpos=a+1 lastpos=a If startpos=Len(s$) Then Goto Exit_instrlast Delay 10 Goto repeat_instrlast EndIf .Exit_instrlast Return lastpos End Function --v

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Tuesday, 30 October 2018, 14:59
zzoom	Nice work, thanks for sharing.

Extract image width+height without loading - bb3d

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