Crop Image with Memblocks - GameCreators Forum

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IronManhood

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Joined: 6th Feb 2015

Location: US

Posted: 25th Jul 2018 20:00 Edited at: 26th Jul 2018 22:52

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I've been working on a function to crop an image but I'm stuck at the moment. This is what is happening on screen:

The function:

// How I'm calling the function. The original image is 1920x1080.
newImgID = CropImage( 1, 0, 0, 1080, 1080 )

function clamp( _val as integer, _min as integer, _max as integer )
	if _val < _min
		exitfunction _min
	elseif _val > _max
		exitfunction _max
	endif
endfunction _val

function CropImage( _imgID, _x, _y, _w, _h )
	if GetImageExists( _imgID ) = 0 then exitfunction 0
	
	_imgWidth = GetImageWidth( _imgID )
	//~ _imgHeight = GetImageHeight( _imgID )
	
	_memFrom = CreateMemblockFromImage( _imgID )
	_memFromMax = GetMemblockSize( _memFrom ) - 4
	
	_memToSize = ( ( _w * _h ) * 4 ) + 12
	_memTo = CreateMemblock( _memToSize )
	_memToMax = _memToSize - 4
	
	// Set header.
	SetMemblockInt( _memTo, 0, _w )
	SetMemblockInt( _memTo, 4, _h )
	SetMemblockInt( _memTo, 8, 32 )
	
	_memTo_P = 12
	
	for yy = _y to _h
		for xx = _x to _w
			_memFrom_P = ( xx + ( yy * _imgWidth ) ) * 4
			_memFrom_P = clamp( _memFrom_P, 12, _memFromMax )
			_memTo_P = clamp( _memTo_P, 12, _memToMax )
			
			SetMemblockByte(_memTo, _memTo_P, GetMemblockByte( _memFrom, _memFrom_P ) )
			SetMemblockByte(_memTo, _memTo_P + 1, GetMemblockByte( _memFrom, _memFrom_P + 1 ) )
			SetMemblockByte(_memTo, _memTo_P + 2, GetMemblockByte( _memFrom, _memFrom_P + 2 ) )
			SetMemblockByte(_memTo, _memTo_P + 3, GetMemblockByte( _memFrom, _memFrom_P + 3 ) )
			
			//~ Print_int( "xx: ", xx )
			//~ Print_int( "yy: ", yy )
			//~ Print_int( "_memTo_P: ", _memTo_P )
			//~ Print_int( "_memFrom_P: ", _memFrom_P )
			
			inc _memTo_P, 4
			
			//~ Sync()
			//~ sleep( 750 )
		next xx
	next yy
	
	retImg = CreateImageFromMemblock( _memTo )
	
	DeleteMemblock( _memTo )
	DeleteMemblock( _memTo_P )
	
endfunction retImg

+ Code Snippet


// How I'm calling the function. The original image is 1920x1080.
newImgID = CropImage( 1, 0, 0, 1080, 1080 )

function clamp( _val as integer, _min as integer, _max as integer )
	if _val < _min
		exitfunction _min
	elseif _val > _max
		exitfunction _max
	endif
endfunction _val

function CropImage( _imgID, _x, _y, _w, _h )
	if GetImageExists( _imgID ) = 0 then exitfunction 0
	
	_imgWidth = GetImageWidth( _imgID )
	//~ _imgHeight = GetImageHeight( _imgID )
	
	_memFrom = CreateMemblockFromImage( _imgID )
	_memFromMax = GetMemblockSize( _memFrom ) - 4
	
	_memToSize = ( ( _w * _h ) * 4 ) + 12
	_memTo = CreateMemblock( _memToSize )
	_memToMax = _memToSize - 4
	
	// Set header.
	SetMemblockInt( _memTo, 0, _w )
	SetMemblockInt( _memTo, 4, _h )
	SetMemblockInt( _memTo, 8, 32 )
	
	_memTo_P = 12
	
	for yy = _y to _h
		for xx = _x to _w
			_memFrom_P = ( xx + ( yy * _imgWidth ) ) * 4
			_memFrom_P = clamp( _memFrom_P, 12, _memFromMax )
			_memTo_P = clamp( _memTo_P, 12, _memToMax )
			
			SetMemblockByte(_memTo, _memTo_P, GetMemblockByte( _memFrom, _memFrom_P ) )
			SetMemblockByte(_memTo, _memTo_P + 1, GetMemblockByte( _memFrom, _memFrom_P + 1 ) )
			SetMemblockByte(_memTo, _memTo_P + 2, GetMemblockByte( _memFrom, _memFrom_P + 2 ) )
			SetMemblockByte(_memTo, _memTo_P + 3, GetMemblockByte( _memFrom, _memFrom_P + 3 ) )
			
			//~ Print_int( "xx: ", xx )
			//~ Print_int( "yy: ", yy )
			//~ Print_int( "_memTo_P: ", _memTo_P )
			//~ Print_int( "_memFrom_P: ", _memFrom_P )
			
			inc _memTo_P, 4
			
			//~ Sync()
			//~ sleep( 750 )
		next xx
	next yy
	
	retImg = CreateImageFromMemblock( _memTo )
	
	DeleteMemblock( _memTo )
	DeleteMemblock( _memTo_P )
	
endfunction retImg

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Bengismo

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Joined: 20th Nov 2017

Location: Yorkshire, England

Posted: 25th Jul 2018 20:18 Edited at: 25th Jul 2018 20:18

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Why not use the inbuilt function to do this without memblocks???

https://www.appgamekit.com/documentation/Reference/Image/CopyImage.htm

It allows you to crop an image with one line of code

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Bengismo

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Posted: 25th Jul 2018 20:22

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And you algorithm is wrong...the loop variables are wrong and dont set the destination or start points quite right either

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puzzler2018

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Posted: 25th Jul 2018 20:22 Edited at: 25th Jul 2018 20:24

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Maybe Iron was liking to try for himself cause was curious on how its done.

Saying someone is wrong is not helping - guide Iron in the right direction...

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Bengismo

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Location: Yorkshire, England

Posted: 25th Jul 2018 20:34 Edited at: 27th Jul 2018 21:36

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In that case then....he wont want our help now would he?? Because hes enjoying it so much figuring it out!!.....lol

Letting someone know there is a function to do exactly waht they want is helping. The right direction is to use the function to do it. lol

Ha.... If he does want to know what the errors are (loop variables and destination offsets) then will happily post them up but im thinking its more likely he didnt know that CopyImage also worked as a Cropimage.
Its been asked before on here...

Better to give someone the logical answer then help them learn a long winded overly complex and slower way of doing it.....

EDIT: In case you do want a working version of your function

function CropImage( _imgID, _x, _y, _w, _h )
    if GetImageExists( _imgID ) = 0 then exitfunction 0
     
    _imgWidth = GetImageWidth( _imgID )
     
    _memFrom = CreateMemblockFromImage( _imgID )
     
    _memToSize = ( ( _w * _h ) * 4 ) + 12
    _memTo = CreateMemblock( _memToSize )
     
    // Set header.
    SetMemblockInt( _memTo, 0, _w )
    SetMemblockInt( _memTo, 4, _h )
    SetMemblockInt( _memTo, 8, 32 )
     
     
    for yy = 0 to _h-1
        for xx = 0 to _w-1
            _memFrom_P = 12+ 4*( (xx+_x) + ( (yy+_y) * _imgWidth ) ) 
            _memTo_P = 12+ 4*(xx + yy*_w)
             
            SetMemblockInt(_memTo, _memTo_P, GetMemblockInt( _memFrom, _memFrom_P ) )
            //SetMemblockByte(_memTo, _memTo_P + 1, GetMemblockByte( _memFrom, _memFrom_P + 1 ) )
            //SetMemblockByte(_memTo, _memTo_P + 2, GetMemblockByte( _memFrom, _memFrom_P + 2 ) )
            //SetMemblockByte(_memTo, _memTo_P + 3, GetMemblockByte( _memFrom, _memFrom_P + 3 ) )
             
        next xx
    next yy
     
    retImg = CreateImageFromMemblock( _memTo )

DeleteMemblock( _memFrom )
    DeleteMemblock( _memTo )
     
endfunction retImg

+ Code Snippet

function CropImage( _imgID, _x, _y, _w, _h )
    if GetImageExists( _imgID ) = 0 then exitfunction 0
     
    _imgWidth = GetImageWidth( _imgID )
     
    _memFrom = CreateMemblockFromImage( _imgID )
     
    _memToSize = ( ( _w * _h ) * 4 ) + 12
    _memTo = CreateMemblock( _memToSize )
     
    // Set header.
    SetMemblockInt( _memTo, 0, _w )
    SetMemblockInt( _memTo, 4, _h )
    SetMemblockInt( _memTo, 8, 32 )
     
     
    for yy = 0 to _h-1
        for xx = 0 to _w-1
            _memFrom_P = 12+ 4*( (xx+_x) + ( (yy+_y) * _imgWidth ) ) 
            _memTo_P = 12+ 4*(xx + yy*_w)
             
            SetMemblockInt(_memTo, _memTo_P, GetMemblockInt( _memFrom, _memFrom_P ) )
            //SetMemblockByte(_memTo, _memTo_P + 1, GetMemblockByte( _memFrom, _memFrom_P + 1 ) )
            //SetMemblockByte(_memTo, _memTo_P + 2, GetMemblockByte( _memFrom, _memFrom_P + 2 ) )
            //SetMemblockByte(_memTo, _memTo_P + 3, GetMemblockByte( _memFrom, _memFrom_P + 3 ) )
             
        next xx
    next yy
     
    retImg = CreateImageFromMemblock( _memTo )

    DeleteMemblock( _memFrom )
    DeleteMemblock( _memTo )
     
endfunction retImg

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puzzler2018

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Posted: 25th Jul 2018 21:16

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Your a star lol

Iron - please use the inbuilt function - good work though

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puzzler2018

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Posted: 25th Jul 2018 21:25

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But then - what if Paul didnt put the function - then how would you do it.

Better programmers I feel is learning how things are achieved rather than just using a function - i have done that thousands of times.

Some people want easiness and quickness to get things done and some likes to try to achieve something constructive

Anyway

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Bengismo

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Location: Yorkshire, England

Posted: 25th Jul 2018 21:40

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Puzzler.... how come you didnt post the answer as you have done this 1000's of times?

Constructive.... is posting solutions as I have done....

Thanks for your fantastic input and help this evening though

...

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IronManhood

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Posted: 25th Jul 2018 22:54 Edited at: 25th Jul 2018 23:06

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I didn't know CopyImage also cropped an image. I was curious to know how image cropping worked in case I needed to write some method of doing so. Learning is fun isn't it? (kill me) Throwing image cropping in with CopyImage makes sense from the AppGameKit developers perspective but it doesn't from a user perspective because it makes it harder to find the correct function to use. I suggest that those two are separated into their own functions.

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Scraggle

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Posted: 26th Jul 2018 08:44

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You could take a look at my Image Functions (link in signature), they do this and a lot more.

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Phaelax

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Location: Metropia

Posted: 27th Jul 2018 05:44 Edited at: 27th Jul 2018 05:46

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Wrote this up real quick for ya, haven't tested it. I also have DBP code that can crop an image/sprite by UV manipulation. The benefit of that method is the cropping follows the rotation of the sprite.

+ Code Snippet


// local coordinates of source image
// Returns ID of cropped image
function crop(srcImg, x1, y1, x2, y2)
	src = createMemblockFromImage(srcImg)
	srcWidth = getMemblockInt(src, 0)

	destWidth = x2 - x1
	destHeight = y2 - y1
	size = destWidth*destHeight*4 + 12
	dest = createMemblock(size)
	setMemblockInt(dest, 0, destWidth)
	setMemblockInt(dest, 4, destHeight)
	setMemblockInt(dest, 8, 32)
	
	for x = x1 to x2
		for y = y1 to y2
			srcPos = (y*srcWidth+ x)*4 + 12
			destPos = ((y-y1)*destWidth + (x-x1))*4 + 12
			setMemblockInt(dest, destPos, getMemblockInt(src, srcPos))
		next y
	next x
	
	img = createImageFromMemblock(dest)
	deleteMemblock(src)
	deleteMemblock(dest)

endfunction img

As far as your code goes, the issues I see are:

for yy = _y to _h
for xx = _x to _w

Should probably be:

for yy = _y to _y+_h
for xx = _x to _x+_w

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