Higher quality Image resize - GameCreators Forum

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sladeiw

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Joined: 16th May 2009

Location: UK

Posted: 20th Feb 2011 13:12 Edited at: 20th Feb 2011 13:14

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I am trying to resize (mostly reducing) an image/bitmap and the standard `copy bitmap` or pixel resize methods produce jagged results. I'm trying to get something equivalent to the PaintShop Pro `smart` resize. I tried coding a simple reduce taking averages of 2 or 4 pixels but it didn't really work.

What I'm hoping is that there is some `shortcut` that you could copy & paste an image or sprite and get automatic bilinear resizing.

Speed is not really an issue because it's just to display a thumbnail of an image, so even a dbpro routine would be fine. Or even a code snippet of bilinear (or whatever) filtering to get me started.

Cheers

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CumQuaT

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Location: Tasmania, Australia

Posted: 20th Feb 2011 14:41

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Try downloading GIMP to do it. It's quite good at that sort of thing, and free!

Malevolence: The Sword of Ahkranox
The infinite RPG
http://www.msoa-game.com

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Sven B

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Location: Belgium

Posted: 20th Feb 2011 14:50 Edited at: 20th Feb 2011 14:50

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Image Kit has a command IK Resize Image. It supports bilinear filtering for render targets.

Sven B

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sladeiw

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Posted: 20th Feb 2011 17:25 Edited at: 20th Feb 2011 23:48

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@CumQuaT Thanks, but I need to generate them on-the-fly.

@SvenB Thanks that looks good! Can I just do this:

+ Code Snippet

get image 1,0,0,origX,origY
ik convert to render target 1
ik resize image 1,newX,newY,1
paste image 1,0,0
delete image 1

Or do I have to clean up anything after converting it to a render target? (It does work fine as-is, but I don't write anything 3D or gaming so I'm a bit of a novice in this area)

It's a bit excessive to use a 164kb plugin for a single command though, I'm really trying to limit the `bloat` of using lots of plugins. Would the source for the resize algorithm be fairly simple for me to convert to db?

Edit: This is what I have so far, but it doesn't seem to be very effective.

for x=0 to 100 step 8
  for y=0 to 100 step 8
    box x,y,x+5,y+5
  next y
next x

scale(100,100,60,60)
wait key
end

function scale(xOrig,yOrig,xDest,yDest)

local floorX as float
  local ceilX  as float
  local floorY as float
  local ceilY  as float
  local scaleX as float
  local scaleY as float
  local fracX  as float
  local fracY  as float
  
  scaleX=xOrig/(xDest*1.0)                       `Scaling factor between original & new image size
  scaleY=yOrig/(yDest*1.0)

for x=0 to xDest
    floorX=x*scaleX                              `X coordinate from original image
    ceilX=min(floorX+1.0,xOrig)                  `Keep within original image boundaries
    
    for y=0 to yDest
      floorY=y*scaleY                            `and Y from original image
      ceilY=min(floorY+1.0,yOrig)

p1=point(floorX,floorY)                    `Get 4 pixels from original image
      p2=point(ceilX,floorY)
      p3=point(floorX,ceilY)
      p4=point(ceilX,ceilY)

fracX=floorX-int(floorX)                   `Weighting of floor/ceiling pixels
      fracY=floorY-int(floorY)

r1=(rgbr(p1)*(1.0-fracX))+(rgbr(p2)*fracX) `Interpolated pixel 1st row
      r2=(rgbr(p3)*(1.0-fracX))+(rgbr(p4)*fracX) `and 2nd
      r=(r2*(1.0-fracY))+(r1*fracY)              `Combined rows

g1=(rgbg(p1)*(1.0-fracX))+(rgbg(p2)*fracX)
      g2=(rgbg(p3)*(1.0-fracX))+(rgbg(p4)*fracX)
      g=(g2*(1.0-fracY))+(g1*fracY)

b1=(rgbb(p1)*(1.0-fracX))+(rgbb(p2)*fracX)
      b2=(rgbb(p3)*(1.0-fracX))+(rgbb(p4)*fracX)
      b=(b2*(1.0-fracY))+(b1*fracY)

ink rgb(r,g,b),0                           `Draw interpolated pixel
      dot x+200,y

ink p1,0                                   `Normal for comparison
      dot x+400,y
    next y
  next x
endfunction

+ Code Snippet

for x=0 to 100 step 8
  for y=0 to 100 step 8
    box x,y,x+5,y+5
  next y
next x

scale(100,100,60,60)
wait key
end


function scale(xOrig,yOrig,xDest,yDest)

  local floorX as float
  local ceilX  as float
  local floorY as float
  local ceilY  as float
  local scaleX as float
  local scaleY as float
  local fracX  as float
  local fracY  as float
  
  scaleX=xOrig/(xDest*1.0)                       `Scaling factor between original & new image size
  scaleY=yOrig/(yDest*1.0)

  for x=0 to xDest
    floorX=x*scaleX                              `X coordinate from original image
    ceilX=min(floorX+1.0,xOrig)                  `Keep within original image boundaries
    
    for y=0 to yDest
      floorY=y*scaleY                            `and Y from original image
      ceilY=min(floorY+1.0,yOrig)

      p1=point(floorX,floorY)                    `Get 4 pixels from original image
      p2=point(ceilX,floorY)
      p3=point(floorX,ceilY)
      p4=point(ceilX,ceilY)

      fracX=floorX-int(floorX)                   `Weighting of floor/ceiling pixels
      fracY=floorY-int(floorY)

      r1=(rgbr(p1)*(1.0-fracX))+(rgbr(p2)*fracX) `Interpolated pixel 1st row
      r2=(rgbr(p3)*(1.0-fracX))+(rgbr(p4)*fracX) `and 2nd
      r=(r2*(1.0-fracY))+(r1*fracY)              `Combined rows

      g1=(rgbg(p1)*(1.0-fracX))+(rgbg(p2)*fracX)
      g2=(rgbg(p3)*(1.0-fracX))+(rgbg(p4)*fracX)
      g=(g2*(1.0-fracY))+(g1*fracY)

      b1=(rgbb(p1)*(1.0-fracX))+(rgbb(p2)*fracX)
      b2=(rgbb(p3)*(1.0-fracX))+(rgbb(p4)*fracX)
      b=(b2*(1.0-fracY))+(b1*fracY)

      ink rgb(r,g,b),0                           `Draw interpolated pixel
      dot x+200,y

      ink p1,0                                   `Normal for comparison
      dot x+400,y
    next y
  next x
endfunction

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Sven B

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Posted: 21st Feb 2011 15:40

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The snippet you posted should be fine. When converting an image to a render target, the original normal image is deleted automatically and it is replaced by the same image but as a render target.

Sven B

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sladeiw

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Joined: 16th May 2009

Location: UK

Posted: 21st Feb 2011 18:17

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Thanks, it does work in a test progam, but I'm using BlueGUI and you can't place the resulting resized image into a panel gadget the same way as a normal image. I'm guessing `render target` images have a different structure or some other differences.

I'd really like to get the algorithm in my last post working if anyone can spot my mistake.

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Green Gandalf

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Playing: Malevolence:Sword of Ahkranox, Skyrim, Civ6.

Posted: 21st Feb 2011 21:49

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Quote: " if anyone can spot my mistake"

Any clues as to what "mistake" we should be looking for?

[Haven't tried your code yet (busy watching pasta cook right now) so this might be obvious when I do.

]

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Grog Grueslayer

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Playing: Green Hell

Posted: 21st Feb 2011 22:04

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Couldn't you save the image made by Image Kit to the HD with the SAVE IMAGE command and reload it in BlueGUI?

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sladeiw

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Joined: 16th May 2009

Location: UK

Posted: 21st Feb 2011 22:43 Edited at: 21st Feb 2011 22:44

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Quote: "Any clues as to what "mistake" we should be looking for?"

I was just in the process of creating an image to illustrate and by looking at the comparison I've solved it. I had the distance fraction reversed in the final Y calculation. The snippet below looks like it works (When compared to PSP8 anyway) Just need to convert it to work directly on memblocks now

for x=0 to 100 step 8
  for y=0 to 100 step 8
    box x,y,x+5,y+5
  next y
next x

scale(100,100,60,60)
wait key
end

function scale(xOrig,yOrig,xDest,yDest)

local floorX as float
  local ceilX  as float
  local floorY as float
  local ceilY  as float
  local scaleX as float
  local scaleY as float
  local fracX  as float
  local fracY  as float
  
  scaleX=xOrig/(xDest*1.0)                       `Scaling factor between original & new image size
  scaleY=yOrig/(yDest*1.0)

for x=0 to xDest
    floorX=x*scaleX                              `X coordinate from original image
    ceilX=min(floorX+1.0,xOrig)                  `Keep within original image boundaries
    
    for y=0 to yDest
      floorY=y*scaleY                            `and Y from original image
      ceilY=min(floorY+1.0,yOrig)

p1=point(floorX,floorY)                    `Get 4 pixels from original image
      p2=point(ceilX,floorY)
      p3=point(floorX,ceilY)
      p4=point(ceilX,ceilY)

fracX=floorX-int(floorX)                   `Weighting of floor/ceiling pixels
      fracY=floorY-int(floorY)

r1=(rgbr(p1)*(1.0-fracX))+(rgbr(p2)*fracX) `Interpolated pixel 1st row
      r2=(rgbr(p3)*(1.0-fracX))+(rgbr(p4)*fracX) `and 2nd
      r=(r1*(1.0-fracY))+(r2*fracY)              `Combined rows

g1=(rgbg(p1)*(1.0-fracX))+(rgbg(p2)*fracX)
      g2=(rgbg(p3)*(1.0-fracX))+(rgbg(p4)*fracX)
      g=(g1*(1.0-fracY))+(g2*fracY)

b1=(rgbb(p1)*(1.0-fracX))+(rgbb(p2)*fracX)
      b2=(rgbb(p3)*(1.0-fracX))+(rgbb(p4)*fracX)
      b=(b1*(1.0-fracY))+(b2*fracY)

ink rgb(r,g,b),0                           `Draw interpolated pixel
      dot x+200,y

ink p1,0                                   `Normal for comparison
      dot x+400,y
    next y
  next x
endfunction

+ Code Snippet

for x=0 to 100 step 8
  for y=0 to 100 step 8
    box x,y,x+5,y+5
  next y
next x

scale(100,100,60,60)
wait key
end


function scale(xOrig,yOrig,xDest,yDest)

  local floorX as float
  local ceilX  as float
  local floorY as float
  local ceilY  as float
  local scaleX as float
  local scaleY as float
  local fracX  as float
  local fracY  as float
  
  scaleX=xOrig/(xDest*1.0)                       `Scaling factor between original & new image size
  scaleY=yOrig/(yDest*1.0)

  for x=0 to xDest
    floorX=x*scaleX                              `X coordinate from original image
    ceilX=min(floorX+1.0,xOrig)                  `Keep within original image boundaries
    
    for y=0 to yDest
      floorY=y*scaleY                            `and Y from original image
      ceilY=min(floorY+1.0,yOrig)

      p1=point(floorX,floorY)                    `Get 4 pixels from original image
      p2=point(ceilX,floorY)
      p3=point(floorX,ceilY)
      p4=point(ceilX,ceilY)

      fracX=floorX-int(floorX)                   `Weighting of floor/ceiling pixels
      fracY=floorY-int(floorY)

      r1=(rgbr(p1)*(1.0-fracX))+(rgbr(p2)*fracX) `Interpolated pixel 1st row
      r2=(rgbr(p3)*(1.0-fracX))+(rgbr(p4)*fracX) `and 2nd
      r=(r1*(1.0-fracY))+(r2*fracY)              `Combined rows

      g1=(rgbg(p1)*(1.0-fracX))+(rgbg(p2)*fracX)
      g2=(rgbg(p3)*(1.0-fracX))+(rgbg(p4)*fracX)
      g=(g1*(1.0-fracY))+(g2*fracY)

      b1=(rgbb(p1)*(1.0-fracX))+(rgbb(p2)*fracX)
      b2=(rgbb(p3)*(1.0-fracX))+(rgbb(p4)*fracX)
      b=(b1*(1.0-fracY))+(b2*fracY)

      ink rgb(r,g,b),0                           `Draw interpolated pixel
      dot x+200,y

      ink p1,0                                   `Normal for comparison
      dot x+400,y
    next y
  next x
endfunction

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Green Gandalf

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Joined: 3rd Jan 2005

Playing: Malevolence:Sword of Ahkranox, Skyrim, Civ6.

Posted: 21st Feb 2011 23:18

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Quote: "I've solved it"

Good.

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