Creating Gradient Images the Fast and Easy Way

I've been trying to spiff up some forms lately. One way to make an attractive form is to use some graphic elements. I particularly like gradient images, as illustrated in this screen shot (the gradient appears banded in this image but not in the actual form):



So, how to create a gradient image of the desired size and color? Although I could do it dynamically using the VFPX GDIPlusX library as described by Cesar Chalom in various posting on his excellent blog, I decided to simply create an image file and use it as the Picture property of an Image object.

With some help from Cesar's blog, I created a simple program, CreateGradient.PRG, that generates a gradient image with the specified file name, size, and colors. The code is self-explanatory. Note that it expects the GDIPlusX class libraries are in the VFP path.

lparameters tcFileName, ;
  tnHeight, ;
  tnWidth, ;
  tnColor1, ;
  tnColor2
local lnColor1, ;
  lnColor2, ;
  lnMode, ;
  lnFormat, ;
  loSystem, ;
  lcExt, ;
  loBitmap, ;
  loRect, ;
  loGfx, ;
  loGradBrush

* Ensure the parameters were passed.

if vartype(tcFileName) <> 'C' or empty(tcFileName) or ;
  vartype(tnHeight) <> 'N' or vartype(tnWidth) <> 'N'
  error 11
  return .F.
endif vartype(tcFileName) <> 'C' ...

* If colors weren't passed, prompt for them.

if pcount() < 4
  lnColor2 = getcolor(rgb(  0, 128, 255))
  lnColor1 = getcolor(rgb(255, 255, 255))
else
  lnColor1 = tnColor1
  lnColor2 = tnColor2
endif pcount() < 4

* This assumes a horizontal gradient. Set lnMode to a different
* value for other types.

lnMode = 0


* Create a GDIPlusX System object.

loSystem = newobject('xfcSystem', 'System.vcx')
with loSystem.Drawing

* Determine the image type from the file extension.

  lcExt = upper(justext(tcFileName))
  do case
    case lcExt = 'PNG'
      lnFormat = .Imaging.ImageFormat.Png
    case lcExt = 'BMP'
      lnFormat = .Imaging.ImageFormat.Bmp
    case lcExt = 'GIF'
      lnFormat = .Imaging.ImageFormat.Gif
    case inlist(lcExt, 'JPG', 'JPEG')
      lnFormat = .Imaging.ImageFormat.Jpeg
    case lcExt = 'ICO'
      lnFormat = .Imaging.ImageFormat.Icon
    case inlist(lcExt, 'TIF', 'TIFF')
      lnFormat = .Imaging.ImageFormat.Tiff
    case lcExt = 'WMF'
      lnFormat = .Imaging.ImageFormat.Wmf
    otherwise
      error 11
      return .F.
  endcase

* Create a bitmap and a rectangle of the desired size.

  loBitmap = .Bitmap.New(tnWidth, tnHeight)
  loRect   = .Rectangle.New(0, 0, tnWidth, tnHeight)

* Create a graphics object.

  loGfx = .Graphics.FromImage(loBitmap)
  loGfx.Clear(.Color.White)

* Create a linear gradient brush.

  loGradBrush = .Drawing2D.LinearGradientBrush.New(loRect, ;
    .Color.FromRgb(lnColor1), .Color.FromRgb(lnColor2), lnMode)

* Fill the rectangle with the gradient brush.

  loGfx.FillRectangle(loGradBrush, loRect)

* Save the image to the specified file.

  loBitmap.Save(tcFileName, lnFormat)
endwith
return

Thanks to Craig Boyd, Bo Durban, and Cesar for all the work they've done on this incredible library!