Pixel color

[honkytonk]

Good morning all
This function (taken here, thanks)

 function GetPixelValue$(x, y)
   #t.m, "getbmp gpv "; x; " "; y; " "; 1; " "; 1
   bmpsave "gpv", "getpvaluetemp.bmp"
   open "getpvaluetemp.bmp" for input as #gpv
   s$ = input$(#gpv, lof(#gpv))
   close #gpv
   if asc(mid$(s$, 29, 1)) = 32 then
       red = asc(mid$(s$, 69, 1))
       green = asc(mid$(s$, 68, 1))
       blue = asc(mid$(s$, 67, 1))
   end if
   GetPixelValue$ = str$(red)+" "+str$(green)+" "+str$(blue)
   kill "getpvaluetemp.bmp"
   unloadbmp "gpv"
 end function

Returns the RGB of a displayed pixel.
But would there be a way to apply it to a bmp in memory (not displayed) or in file?
Thank you for.

[tsh73]

What are you trying to do?

How stuff is stored in BMP is known (there are several formats due to color depth but we can agree to use one that Just BASIC saves with BMPSAVE - 32 bit)

so one can read bitmap header - get image dimensions - use them to calculate point in a file - load 3 bytes from it, get the color.

I have old code that reads all pixels from the file (and draws it)
I just run it - it works for me
You can start from here.

as for bmp in memory - is it a bmp read from file?
then there is no much difference.

But if you hope to work with bmp loaded in JustBASIC with LOADBMP or captured with GETBMP - I'm afraid there is no way (except using from file)
'read BMP pixel by pixel
'by tsh73
'compiled from various sources (sources in C and QB) to Just Basic 1.01
'10 May 2007
'released to public domain
' - to all Just Basic users who find this interesting (or useful)
'(+):   fixed 25 11 2017 for offset not (%4 == 0)

'all color depths I've seen (1, 4, 8 and 24)
'no compression
'examples created by Gimp from very old file of unknown origin YROSE.JPG

filedialog "Open BMP file", "*.bmp", fname$
open fname$ for binary as #1
print "File "+stripPath$(fname$) +" length is ";lof(#1)

print " ======= BMPHeader ============"
print "ValidID (first 2 bytes) is: (should be BM)";tab(45);readStr$(2)
print "fileSize";tab(45);readLong()
print "reserved";tab(45);readLong()
offset = readLong()
print "offset";tab(45);offset
print " ======= WindowsInfoHeader ==========="
print "SizeOfHeader (should be 40)";tab(45); readLong()
BMwidth = readLong()
print "width";tab(45); BMwidth
BMheight = readLong()
print "height";tab(45); BMheight
print "planes (should be 1)" ;tab(45);read2Bytes()
bpp = read2Bytes()
print "BitsPerPixel (bpp)";tab(45); bpp
CompressMethod = readLong()
print "CompressMethod";tab(45); CompressMethod;" ";word$("Uncompressed|8 Bit RLE Compression|4 Bit RLE Compression|bi_bitfields",CompressMethod+1,"|")
imagebytes = readLong()
print "imagebytes";tab(45); imagebytes
print "xres";tab(45);  readLong()
print "yres";tab(45);  readLong()
colch = readLong()
print "ColorsUsed";tab(45); colch  ' could be 0 - All Used
print "ImportantColors";tab(45);  readLong()

print " ======= calculated info ==========="
currPos = LOC(#1)
print "curr pos is ";tab(45);currPos
print "for palette left ";tab(45); offset - currPos
print "for palette colors ";tab(45); (offset - currPos)/4
' ==  colch
if colch = 0 then colch = (offset - currPos)/4  '???
'because it could be 0 - All Used
print "imagebytes + offset " ;tab(45); imagebytes + offset

byteWidth = BMwidth*bpp/8
if int(byteWidth)<> byteWidth then byteWidth= int(byteWidth)+1
actualWidth = byteWidth
if actualWidth mod 4 <>0 then  actualWidth = actualWidth + 4-actualWidth mod 4
'padded to 4 bytes
print "line length in bytes ";tab(45);actualWidth
print "imagebytes / line length in bytes ";tab(45);imagebytes / actualWidth

if inlist(CompressMethod, "1,2")  then
   print "Compressed bitmaps (RLE encoding) are not supported"
   close #1
   end
end if

if not(inlist(bpp,"1,4,8,16,24,32")) then
   print "Color depth (bits per pixel, bpp) other then 1,4,8,16,24,32 is not supported"
   close #1
   end
end if

if  colch = 0 then
   print " ======= No palette present ==========="
   goto [skipPalette]
end if

'** palette goes here
dim rpal(255),gpal(255),bpal(255),spal$(255)
for i = 0 to colch-1
   bpal(i) = readByte()
   gpal(i) = readByte()
   rpal(i) = readByte()
   spal$(i) = str$( rpal(i))+" "+str$( gpal(i))+" "+str$( bpal(i))
   'print  spal$(i)
   dummy$ = input$(#1, 1)  'skip one byte
   if i >=255 then exit for
next i

seek #1, offset

if CompressMethod = 3 then
   print "Color masks are:"
   i = 0
   redMask = ((rpal(i)*256)+ gpal(i))*256+ bpal(i)
   print "Red";  tab(8); hex$(redMask)
   i = 1
   greenMask = ((rpal(i)*256)+ gpal(i))*256+ bpal(i)
   print "green";tab(8); hex$(greenMask)
   i = 2
   blueMask = ((rpal(i)*256)+ gpal(i))*256+ bpal(i)
   print "blue"; tab(8); hex$(blueMask)
end if

'show palette
WindowWidth = 400
WindowHeight = 400
open "Palette" for graphics_nf_nsb as #pal
print #pal, "trapclose [endPalette]"

for i =0 to 15
   for j =0 to 15
       y = i*20+20
       x = j*20+20
       x1 = x+15
       y1 = y+15
       ind = i*16+j
       if ind > colch-1 then exit for
       print #pal, "backcolor ";spal$(ind)
       print #pal, "up"
       print #pal, "goto ";x;" ";y
       print #pal, "down"
       print #pal, "boxfilled ";x1;" ";y1

   next j
   if ind > colch-1 then exit for
next i
print #pal, "flush"      'make the graphics stick
print " ======= palette present ==========="
print colch; " colors"
print "close palette window to view image"
wait

[endPalette]
close #pal

[skipPalette]

startTime = time$("ms")
'** now the picture itself...
WindowWidth = BMwidth+8 ' + window border
'WindowHeight = BMheight+20  ' + window header, win2000 style
WindowHeight = BMheight+34  ' + window header, XP style
open "picture" for graphics_nf_nsb as #gr1
'print #gr1, "trapclose Quit"
print #gr1, "trapclose [gr1End]"
print #gr1, "down"       'ready to draw
print #gr1, "north ; turn 90"

oldInd = 999    'magic
FOR y =  BMheight-1 TO 0 step -1           ' Countdown for upsidedown image
   aLine$ = readStr$(actualWidth)
   print #gr1, "place 0 ";y
   FOR x = 0 TO BMwidth-1
   select case bpp
   case 1
       byte = asc(mid$( aLine$, int(x/8)+1, 1))
'        pos = 7 - x mod 8
'        pow2 = 2^pos
'        if (byte and pow2) <> 0 then
'            ind = 1
'        else
'            ind = 0
'        end if
       ind = ((byte and (2^(7 - x mod 8))) <> 0)
       if oldInd <> ind then
           print #gr1, "color "; spal$(ind)
           oldInd = ind
       end if
       print #gr1, "go 1"
   case 4
       byte = asc(mid$( aLine$, int(x/2)+1, 1))
       if x mod 2 <> 0 then
           ind = byte mod 16
       else
           ind = int(byte / 16)
       end if
       if oldInd <> ind then
           print #gr1, "color "; spal$(ind)
           oldInd = ind
       end if
       print #gr1, "go 1"
   case 8
       ind = asc(mid$( aLine$, x+1, 1))
       if oldInd <> ind then
           print #gr1, "color "; spal$(ind)
           oldInd = ind
       end if
       print #gr1, "go 1"

   case 16
       bytes = byte2Num(mid$( aLine$, 2*x+1, 2))
       'if  CompressMethod = 3 then
           r =  (bytes AND redMask) /256
           g =  (bytes AND greenMask) / 32 * 4
           b =  (bytes AND blueMask) * 8
       'end if
       print #gr1, "color ";r;" ";g;" ";b
       print #gr1, "go 1"
   case 24
       r = asc(mid$( aLine$, 3*x+3, 1))
       g = asc(mid$( aLine$, 3*x+2, 1))
       b = asc(mid$( aLine$, 3*x+1, 1))
       print #gr1, "color ";r;" ";g;" ";b
       print #gr1, "go 1"
   case 32
       r = asc(mid$( aLine$, 4*x+3, 1))
       g = asc(mid$( aLine$, 4*x+2, 1))
       b = asc(mid$( aLine$, 4*x+1, 1))
       print #gr1, "color ";r;" ";g;" ";b
       print #gr1, "go 1"
   end select
   NEXT x
next y

print #gr1, "flush"      'make the graphics stick
'print #gr1, "redraw"
endTime=time$("ms")
print
print "Drawing BMP (not incl. palette) took ";
print endTime-startTime; " milliseconds"
close #1

wait

[gr1End]
close #gr1

end

' some functions ********************************************8
function readByte()
   readByte = asc(input$(#1, 1))
end function

function readLong()
   readLong = byte2Num(input$(#1, 4))
end function

function read2Bytes()
   read2Bytes = byte2Num(input$(#1, 2))
end function

function readStr$(n)
    readStr$ = input$(#1, n)
end function

function byte2Num(c$)
   res = 0
   for i = len(c$) to 1 step -1    'lower byte first
       res = res * 256+asc(mid$(c$,i,1))
   next i
   byte2Num = res
end function

function stripPath$(fname$)
   found = 0
   for i = len(fname$) to 1 step -1
       c$=mid$(fname$,i,1)
       'print i; c$,
       if c$="\" then
           found = 1
           exit for
       end if
   next i
   if found then
        stripPath$ = mid$(fname$,i+1)
   else
       stripPath$ = fname$
   end if
end function

function inlist(aVal, list$)
   list$ = ","+list$+","
   inlist = (instr(list$, ","+str$(aVal)+",")<>0)
end function

Function hex$(n)
   h$ = ""
   do
       h$ = mid$("0123456789ABCDEF", (n mod 16)+1, 1) + h$
       n = int(n/16)
   loop while n > 0
   hex$ = h$
End Function


[honkytonk]

I try to modify a bmp according to its colors, and the processing time depends on the dimensions, the bigger it is the longer it is; So I would like to reduce the time if possible.
Thanks a lot for your code, I will see what I can do with it.

EDIT: Wow ! It is very complex.
It will take a lot of thinking to understand everything.
Thank you again TSH73 Anatoly.

[tenochtitlanuk]

Over the years I've had a lot of fun modifying images. Many examples on my website. I use method of Anatoly on bmps, and also in LB use getpixel.

Example

But recently I found the following much easier method... use ppm images.

I particularly recommend you use your painting package ( I use the free GIMP) to save your images as *.ppm, in 'raw' format. These are like bmp files in having each pixel stored as three RGB bytes, but have a MUCH simpler introductory section. You read it as a file, usually into a 2D array, then read the coloured pixels and do what you like on them... it's the fastest way I have found in JB/LB.
You only need to display the altered pixels on-screen if you like watching or are testing- setting pixels will slow the conversion down a LOT.

You can always load the altered image back into GIMP and re-save as jpg or gif depending on what you want to do with it.

link

[honkytonk]

Nov 25, 2020 9:44:55 GMT tenochtitlanuk said:

Over the years I've had a lot of fun modifying images. Many examples on my website. I use method of Anatoly on bmps, and also in LB use getpixel.

Example

But recently I found the following much easier method... use ppm images.

I particularly recommend you use your painting package ( I use the free GIMP) to save your images as *.ppm, in 'raw' format. These are like bmp files in having each pixel stored as three RGB bytes, but have a MUCH simpler introductory section. You read it as a file, usually into a 2D array, then read the coloured pixels and do what you like on them... it's the fastest way I have found in JB/LB.
You only need to display the altered pixels on-screen if you like watching or are testing- setting pixels will slow the conversion down a LOT.

You can always load the altered image back into GIMP and re-save as jpg or gif depending on what you want to do with it.

link

Regarding your example:
LB is much more powerful (by access to DLLs) than JB, but I prefer to stay with JB to allow access to beginners, who start with JB.
And I prefer also to stay in the ".BMP" format, the only one recognized by JB.

[Rod]

This is just a rehash of Anatoly's binary file access method. I have tried to keep it simple. One learning point is that you need to close the file before the last write is recorded. The code updates all pixels or allows fast set pixel and get pixel access. I use global Red Green Blue variables to retrieve the color data very much like MouseX MouseY etc.

This should really copy the supplied bmp, it does not so it will trash any .bmp you give it so feed it a copy .bmp.


   WindowWidth  = 700
   WindowHeight = 400
   UpperLeftX   = (DisplayWidth-WindowWidth)/2
   UpperLeftY   = (DisplayHeight-WindowHeight)/2
   graphicbox #1.gb1,10,10,300,300
   graphicbox #1.gb2,330,10,300,300
   open "SET GET Pixel" for graphics_nf_nsb as #1
   #1 "trapclose [quit]"
   global bmpw,bmph,padding,offset,bytes,Blue,Green,Red




   [loadbmp]
       filedialog "Choose an image","*.bmp",file$
       if file$<>"" then
           'display the original bmp in gb1
           loadbmp "original",file$
           #1.gb1 "down ; drawbmp original 0 0"

           'now open the same bmp file for binary read/write access
           open file$ for binary as #bmp

           'analyse the file header bytes
           seek #bmp,10 'picture data offset, where the color data starts 4 bytes of data
           offset=asc(input$(#bmp,1))+asc(input$(#bmp,1))*256+asc(input$(#bmp,1))*65536+asc(input$(#bmp,1))*16777216
           seek #bmp,18 'width 4 bytes of data
           bmpw=asc(input$(#bmp,1))+asc(input$(#bmp,1))*256+asc(input$(#bmp,1))*65536+asc(input$(#bmp,1))*16777216
           seek #bmp,22 'height 4 bytes of data
           bmph=asc(input$(#bmp,1))+asc(input$(#bmp,1))*256+asc(input$(#bmp,1))*65536+asc(input$(#bmp,1))*16777216
           seek #bmp,28 'bits per pixel, ie color depth 2 bytes of data
           bits=asc(input$(#bmp,1))+asc(input$(#bmp,1))*256

           'work out start of picture data and how to move through file
           pointer=offset

           'work out how many bytes in the bits per pixel 24=3 bgr 32=4 abgr
           bytes=bits/8

           'work out padding each raster line must be a 4byte multiple
           mult=bits/8*bmpw/4
           padding = 4*(1-(mult-int(mult))) mod 4
           close #bmp

       end if

   [setall]
       'this demo updates every pixel of the image
       open file$ for binary as #bmp

       for y=1 to bmph
           for x=1 to bmpw

               'run through binary file data moving the file pointer as we go
               seek #bmp, pointer

               'get pixel color stored as BGR Liberty needs RGB
               b=asc(input$(#bmp,1))
               g=asc(input$(#bmp,1))
               r=asc(input$(#bmp,1))

               'change the color
               r=r-150
               if r<0 then r=0

               'set pixel color
               'because we read three bytes we need to set the file pointer back
               seek #bmp, pointer
               #bmp chr$(b);chr$(g);chr$(r);

               'move on
               pointer=pointer+bytes
           next

           'add padding at end of raster line
           pointer=pointer+padding
       next

       'note we need to close the file to have Windows
       'write the last update
       close #bmp
       gosub [show]

   [setpixel]
       'this demo sets individual pixels via function setpixel()
       'open temporary file for read and write access
       open file$ for binary as #bmp
       for n=0 to bmpw-1 'zero index
           null=setpixel(n,n,0,0,0) 'x,y,r,g,b
       next
       close #bmp
       gosub [show]

   [getpixel]
       'this demo retrieves the RBG of a pixel via function getpixel()
       'open temporary file for read and write access
       open file$ for binary as #bmp
       'run along top line
       for n=0 to bmpw-1 'zero index
           null=getpixel(n,0) 'x,y
           'the global RGB variables are filled
           print Red,Green,Blue
       next
       close #bmp

       wait


   [show]
       'show what we did, load file as bmp and display
       loadbmp "newfile",file$
       #1.gb2 "down ; drawbmp newfile 0 0"
       return

   [quit]
       close #1
       end


       function setpixel(x,y,r,g,b)
           'raster lines are stored bottom up so we invert y
           y=(bmph-1)-y
           pointer=offset+x*bytes+y*(bmpw*bytes+padding)
           'set pixel color
           seek #bmp, pointer
           #bmp chr$(b);chr$(g);chr$(r);
       end function

       function getpixel(x,y)
           'raster lines are stored bottom up so we invert y
           y=(bmph-1)-y
           pointer=offset+x*bytes+y*(bmpw*bytes+padding)
           'get pixel color stored as BGR Liberty needs RGB
           seek #bmp, pointer
           Blue=asc(input$(#bmp,1))
           Green=asc(input$(#bmp,1))
           Red=asc(input$(#bmp,1))
       end function



[Enzo]

This is all the code needed to load bmp data to either an array or memory, or am I missing something? I am trying to store bmp data in a string$ = "DATAFORMAT" to include images in my program while not having the user download the .bmp file, or a self unpacking .exe

global n, bmpw, y, pointer, offset, x, bytes, y, bmpw, padding, Red, Blue, Green
function file$(file$)
       open file$ for binary as #bmp
       for n=0 to bmpw-1 'zero index
           null=getpixel(n,0) 'x,y
                       'print Red,Green,Blue
       next
       close #bmp
end function
       function getpixel(x,y)
           y=(bmph-1)-y
           pointer=offset+x*bytes+y*(bmpw*bytes+padding)
           seek #bmp, pointer
           Blue=asc(input$(#bmp,1))
           Green=asc(input$(#bmp,1))
           Red=asc(input$(#bmp,1))
       end function


I was simply going to have it output to a mainwin as;

for x = 1 to numberofbmps
bmpfiledata$=file$(str$(x)".bmp") 'files 1-20   1.bmp 2.bmp ect.
print "string$(x)="";bmpfiledata$;"""
next x


[Rod]

Yes that’s probably all the code you need to open the .bmp. However you need to know the header info to fill the global variables correctly. Also you need the header data at the head of the file if you want to make it a .bmp and load and display it. If the bmps are all the same size and color depth it’s doable.