PowerBuilder – Get Color Value of Pixel under Pointer
Here is a sample application which will give you the color value of the pixel the user clicked on on a picture control (this can be used for any object inherited from a dragobject). To see the list of draggable controls, open the Browser. All the objects in the hierarchy below dragobject are draggable. This functionality can be used to ‘prettyfy’ a report selection window by providing an irregular bitmap (sales region map, delivery routes, etc.) within which the user clicks. Depending upon the color they choose, a separate report is produced.
Anyway, the functionality is encapsulated in an nvo and involves three API external functions.
FUNCTION ulong GetPixel(ulong hwnd, long xpos, long ypos) LIBRARY "Gdi32.dll" // get device context - required for graphic stuff FUNCTION ulong GetDC(long hwnd) LIBRARY "user32.dll" FUNCTION long ReleaseDC (long hwnd, ulong hDC) LIBRARY "user32.dll"
The function is called of_get_color. It accepts a dragobject by reference.
long ll_xpos, ll_ypos ulong ul_rtn ulong ul_handle, ul_device // get handle ul_handle = handle(a_object) ul_device = GetDC(ul_handle) // get position of pointer ll_xpos = UnitsToPixels(a_object.PointerX(), XUnitsToPixels!) ll_ypos = UnitsToPixels(a_object.PointerY(), YUnitsToPixels!) ul_rtn = GetPixel(ul_device, ll_xpos, ll_ypos) ReleaseDC( ul_handle, ul_device) RETURN ul_rtn
On the window there is an event which is triggered when the user clicks on an appropriate object.
int li_r, li_b, li_g ulong lul_color n_pixelcolor lnv_color lul_color = lnv_color.of_get_color(a_object) //max value of unsigned long indicates error IF lul_color = 4294967295 THEN r_1.fillcolor = 0 st_ul.text = 'Invalid Color' st_rgb.text = '' RETURN END IF // get RGB values li_r = mod(lul_color,256) li_g = mod((lul_color / 256), 256) li_b = mod ((lul_color / 65536), 256) st_ul.text = 'U Long: ' + string(lul_color) st_rgb.text = 'RGB( ' + string(li_r) + ', ' + string(li_g) + ', ' + string(li_b) + ')' st_rgb.textcolor = RGB(li_r,li_g,li_b) //just to prove the values are correct r_1.fillcolor = lul_color
The window displays the color value as well as its derived RGB values.
Pixel Color App
Color clicked on.
The code is in PB11.5.1. A zip file with the .pbl and appropriate exports can be found here.
Special thanks to Roland Smith of TeamSybase.
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