# Algo needed for 'Fit to page'

This is a discussion on Algo needed for 'Fit to page' within the Windows Programming forums, part of the Platform Specific Boards category; Hello Hi, sorry for just dropping in... Does anyone know how to calculate a 'Fit To Page' thing when printing. ...

1. ## Algo needed for 'Fit to page'

Hello

Hi, sorry for just dropping in... Does anyone know how to calculate a 'Fit To Page' thing when printing.

I don't need no source. Just the basic equation would be great.

TIA,
Jim

2. Take a look at Petzold's Book Programming Windows. It has several ways of printing using Windows API.

- Sean

3. Sean,

I know how to print.. and I read Petzold a long time ago. My problem is mathematics

I do have the the widths and heights (let's call them

bmp.x *** width of the bitmap
bmp.y *** height of the bitmap
pd.x *** width of the printer DC
pd.y *** height of the printer DC

I just need to figure out that if I take the longest side of the bitmap (ex: width) and set this side the same value as the printers width. how to calculate the propper porpotion of it's lenght for the printer. Considering that sometimes the bitmap needs to be shrinked and sometimes enlarged.

Like saying the width of the bitmap (20000 pixels) == width of the printer (7000 pixels) So shrink it by 13000 pixels) Which is ??% of it. Considering this I need to shrink the height by the same amount of % to keep the propper porpotions.

How do I do % calculations like this manually ? Using Divide, Substraction and Multiplication.

Wish I had paid more attention in school that day

4. Forget it

I just posted my answer myself... ( LOL )

IF bmp.x > pd.x
percentage.to.shrink = (bmp.x/100)*(bmp.x-pd.x)

ELSE
percentage.to.enlarge = (bmp.x/100)*(pd.x-bmp.x)

ENDIF

5. Here I post my 'pseudo code' in case someone ever needs 'Fit-To-Page' calculations... Of course this is mostly assumptions, but it looks pretty correct atm.

Code:
```///
bmp.x == width of bitmap
bmp.y == height of bitmap
pd.x == pd.original.width == printerDC.width
pd.y == pd.original.height == printerDC.height
///

.IF bmp.x > bmp.y

.IF bmp.x >= pd.x

percentage.to.enlarge == (bmp.x/100) * (bmp.x - pd.x)
pixels == (bmp.y/100)*percentage.to.enlarge)
pd.y == bmp.y + pixels

.ELSE

percentage.to.shrink == (bmp.x/100) * (pd.x - bmp.x)
pixels == (bmp.y/100)*percentage.to.shrink)
pd.y == bmp.y - pixels

.ENDIF
////at this point we can be sure that the width is fitting !
.IF pd.y > pd.original.height
percentage.to.shrink == (pd.original.height/100)*(pd.y-pd.original.height)
pixels == (pd.y/100)*percentage.to.shrink
pd.y == pd.y - pixels
pixels == (pd.x/100)*percentage.to.shrink
pd.x == pd.x - pixels
.ENDIF

.ELSE

.IF bmp.y >= pd.y

percentage.to.enlarge == (bmp.y/100) * (bmp.y - pd.y)
pixels == (bmp.x/100)*percentage.to.enlarge)
pd.x == bmp.x + pixels

.ELSE

percentage.to.shrink == (bmp.y/100) * (pd.y - bmp.y)
pixels == (bmp.x/100)*percentage.to.shrink)
pd.x == bmp.x - pixels

.ENDIF

////at this point we can be sure that the height is fitting !
.IF pd.x > pd.original.width
percentage.to.shrink == (pd.original.width/100)*(pd.x - pd.originalwidth)
pixels == (pd.x/100)*percentage.to.shrink
pd.x == pd.x - pixels
pixels == (pd.y/100)*percentage.to.shrink
pd.y == pd.y - pixels
.ENDIF

.ENDIF```
If someone sees an error feel free to correct :-P

6. Using StretchBlt() is slow and unlikely to give required results unless an integer multiplier is used.

A better solution is to use Coordinate Space Transformations.

Experiment with this code (will fail if iImageWidth or iImageHeight is greater than the client area)

Code:
```SetGraphicsMode(hdc, GM_ADVANCED);//only works with WIN2000 (not for WIN98)
SetMapMode(hdc,MM_ISOTROPIC);//preserve image ratio
SetWindowExtEx   (hdc, iWidth, iHeight, NULL) ;//the arbitrary scale to use
SetViewportExtEx (hdc, iActualWidth, iActualHeight, NULL) ;//the actual client area

xForm.eM11 = (FLOAT) iRatio; //set the ratio to change image size
xForm.eM12 = (FLOAT) 0.0;
xForm.eM21 = (FLOAT) 0.0;
xForm.eM22 = (FLOAT) iRatio;
xForm.eDx  = (FLOAT) 0.0;
xForm.eDy  = (FLOAT) 0.0;

SetWorldTransform(hdc, &xForm);

//calc the margins (could fail here)
Rect.left=((ClientRect.right-ClientRect.left)- iImageWidth)/2;
Rect.top=((ClientRect.bottom-ClientRect.top)- iImageHeight)/2;
Rect.right= Rect.left +iImageWidth;
Rect.bottom= Rect.top+iImageHeight;

//convert to DC scale
DPtoLP (hdc, &Rect, 2) ;

//draw the rect to show image size
hBrush=CreateSolidBrush(RGB(0,0,0));//black brush
hSysBrush=SelectObject(hdc,hBrush);
FrameRect(hdc,&Rect,hBrush);
SelectObject(hdc,hSysBrush);
DeleteObject(hBrush);```

7. Novacain,

Thanks for the reply. But even tho that I developp this app for XP I try to keep it downwards compatible. (Also because I refuse to put anything else then 98SE on my developpment box :grin: )

Actually I don't use StretchBlt but iPicture::Render for the job as I blend a JPG onto the PrintersDC but it's basically the same as StretchBlt.

Anyway, I play around with your code for awhile and see how far I get

Regards,
Jim