SCALE AND SHEAR WITH GDI+

Execute the code below to change shear and scale of an image.

Special thanks to Anatolyi Mogylevets, from www.news2news.com
A great part of this code comes from him, once _GdiPlus.vcx is incomplete, what obliges us to call directly through API http://www.news2news.com/vfp/?example=479

 

To better understand how scale and shear work with GDI+, take a look at these links as well:
http://www.vbaccelerator.com/home/vb/code/vbmedia/using_gdi_plus/scale__rotate__skew_and_transform_images/article.asp
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/gdicpp/gdiplus/gdiplusreference/classes/matrixclass/matrixmethods/shear.asp
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/gdicpp/gdiplus/gdiplusreference/classes/matrixclass/matrixmethods/shear.asp

* Scale and Shear with GDI+
* --------------------------
* special thanks to Anatolyi Mogylevets, from www.news2news.com
* a great part of this code comes from him, once _gdiplus.vcx
* is still incomplete what obliges us to call directly through Win32Api
* http://www.news2news.com/vfp/?example=479

declare integer gdipcreatematrix in gdiplus integer @matrix
declare integer gdipdeletematrix in gdiplus integer matrix
declare integer gdipshearmatrix in gdiplus;
        integer matrix, single shearx, single sheary, integer ord
declare integer gdipscalematrix in gdiplus;
        integer matrix, single scalex, single scaley, integer ord
declare integer gdipsetworldtransform in gdiplus;
        integer graphics, integer matrix

lcSource = GETPICT("jpg;gif;bmp")
lcDestination = addbs(justpath(lcSource))+ "sheared_" +;
   juststem(lcSource)+".jpg"
local loImage as gpimage of _gdiplus.vcx
loImage = newobject("gpimage", home() + "ffc/_gdiplus.vcx")
loImage.createfromfile(lcsource)

local loBitmap as gpbitmap of _gdiplus.vcx
loBitmap = newobject("gpbitmap", home() + "ffc/_gdiplus.vcx")
local lographics as gpgraphics of _gdiplus.vcx
loGraphics = Newobject('gpgraphics',home() + "ffc/_gdiplus.vcx")

*** now we create a new image with
*** create method - creates a bitmap object.
*** syntax: ? this.create(tnwidth, tnheight[, tnpixelformat])
*** tnpixelformat, optional, one of gdiplus_pixelformat_* constants,
*** defaults to gdiplus_pixelformat_32bppargb.

local lnWidth, lnHeight, lnPixelFormat
lnWidth = loimage.imagewidth
lnHeight = loimage.imagewidth
lnPixelFormat = loImage.PixelFormat
local matrix1, xScaleFactor, yScaleFactor, xShearFactor, yShearFactor
xScaleFactor = 1.30
yScaleFactor = 0.75

xShearFactor = 0.20
yShearFactor = 0.10

store 0 to matrix1

lnNewWidth  = lnWidth  * xScaleFactor * (1 + xShearFactor)
lnNewHeight = lnHeight * yScaleFactor * (1 + yShearFactor)

loBitmap.Create(lnNewWidth, lnNewHeight, lnPixelFormat)
loGraphics.Createfromimage(loBitmap)

* Create matrix object
* and apply scale and shear transformations
= gdipCreateMatrix(@matrix1)
= gdipScaleMatrix(matrix1, xscalefactor, yscalefactor, 0)
= gdipShearMatrix(matrix1, xshearfactor, yshearfactor, 0)
= gdipSetWorldTransform(lographics.gethandle(), matrix1)
lographics.DrawImageAt(loimage, 0, 0)
lographics.ResetTransform()
= gdipdeletematrix(matrix1)

loBitmap.SavetoFile(lcDestination, "image/jpeg")