CROP IMAGES WITH GDI+

Cropping an image is a simple task for Gdiplus.
One of the ways that this can be done is using the GDI+ function gdipclonebitmapareai , that unfortunately was not included in _Gdiplus.vcx, but can be easily accessed.

Original Image

Top Left	Center	Bottom Right

Run the code below, selecting any image, and you will see the image cropped in three ways: the top-left part of the image, the bottom-right part, and the center.

LOCAL lcSource      
lcSource = GETPICT()
IF EMPTY(lcSource)       
   RETURN      
ENDIF 
* Load image to GDI+       
LOCAL loImage AS gpImage OF HOME() + ffc/_gdiplus.vcx      
loImage = NEWOBJECT("gpImage",HOME()+"ffc/_gdiplus.vcx")      
loImage.CreateFromFile(lcSource)      
lnWidth = loImage.ImageWidth      
lnHeight = loImage.ImageHeight
  
* Crop Image
LOCAL loCropped as gpBitmap OF HOME() + ffc/_gdiplus.vcx
* Crop TopLeft       
loCropped = Crop(loImage, 0, 0, lnWidth / 2, lnHeight /2)      
loCropped.SavetoFile("crop-topleft.png","image/png")      
RUN /n Explorer.exe crop-topleft.png
* Crop BottomRight       
loCropped = Crop(loImage, lnWidth / 2, lnHeight /2, lnWidth /2, lnHeight /2)
loCropped.SavetoFile("crop-bottomright.png","image/png")      
RUN /n Explorer.exe crop-bottomright.png
* CropCenter      
loCropped = Crop(loImage, lnWidth / 4, lnHeight /4, lnWidth /2, lnHeight /2)
loCropped.SavetoFile("crop-center.png","image/png")      
RUN /n Explorer.exe crop-center.png
RETURN
  
PROCEDURE Crop(toImage, x, y, tnWidth, tnHeight, tnPixelFormat)        
IF VARTYPE(tnPixelFormat) = "l"        
   tnPixelFormat = toImage.PixelFormat        
ENDIF 
* gpstatus wingdipapi gdipclonebitmapareai         
* (int x, int y, int width, int height, pixelformat format,          
* gpbitmap *srcbitmap, gpbitmap **dstbitmap)          
DECLARE LONG gdipclonebitmapareai IN gdiplus.dll ;        
   LONG x, LONG y, LONG nwidth, LONG nheight, ;        
   LONG pixelformat, LONG srcbitmap, LONG @dstbitmap        
LOCAL lnNewBitmap        
lnNewBitmap = 0        
= gdipCloneBitmapAreaI(x, y, tnWidth, tnHeight, ;        
tnPixelFormat, toImage.getHandle(), @lnNewBitmap)        
LOCAL loNewImage        
loNewImage = NEWOBJECT("gpBitmap",HOME()+"ffc/_gdiplus.vcx")        
loNewImage.SetHandle(lnNewBitmap)        
RETURN lonewimage        
ENDPROC 

To achieve this, I created a small procedure, "crop", that receives the following parameters retrieved from msdn :

    toimage - image or bitmap object

    x - integer that specifies the x-coordinate of the upper-left corner of the rectangle that specifies the portion of this bitmap to copy.

    y - integer that specifies the y-coordinate of the upper-left corner of the rectangle that specifies the portion of this bitmap to copy.

    width - integer that specifies the width of the rectangle that specifies the portion of this bitmap to copy.

    height - integer that specifies the height of the rectangle that specifies the portion of this image to copy.

    format - optional, integer that specifies the pixel format of the new bitmap. the pixelformat data type and constants that represent various pixel formats are defined in gdiplus.h. for more information about pixel format constants, see image pixel format constants.

    return - this method returns a pointer to the new bitmap object containing the cropped image.