Color of a screen pixel: Difference between revisions
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Revision as of 18:20, 22 May 2011
You are encouraged to solve this task according to the task description, using any language you may know.
Get color information from an arbitrary pixel on the screen, such as the current location of the mouse cursor. The mouse cursor may or may not have to be active in a GUI created by your program. These functions are OS related.
Applesoft BASIC
Low-Resolution (Lo-Res) graphics 40x48 16 colors, page 1 <lang Applesoft BASIC>X = PDL (0) * 5 / 32 Y = PDL (1) * 3 / 16
COLOR= SCRN( X,Y)</lang>
AutoHotkey
<lang AutoHotkey>MouseGetPos, MouseX, MouseY PixelGetColor, color, %MouseX%, %MouseY%</lang>
BASIC
In a graphics mode (for instance, SCREEN 13 or SCREEN 12) <lang qbasic>color = point(x, y)</lang>
BBC BASIC
In BBC BASIC for Windows you can read either the 'logical colour' (palette index) or the 'true colour' (24-bit RGB value). <lang bbcbasic> palette_index% = POINT(x%, y%)
RGB24b_colour% = TINT(x%, y%)</lang>
C
<lang c>
- include <X11/xlib.h>
void get_pixel_color (Display *d, int x, int y, XColor *color) {
XImage *image; image = XGetImage (d, RootWindow (d, DefaultScreen (d)), x, y, 1, 1, AllPlanes, XYPixmap); color->pixel = XGetPixel (image, 0, 0); XFree (image); XQueryColor (d, DefaultColormap(d, DefaultScreen (d)), color);
}
// Your code XColor c; get_pixel_color (display, 30, 40, &c); printf ("%d %d %d\n", c.red, c.green, c.blue); </lang>
(Linux users, see grabc.) <lang c>#include <Windows.h>
COLORREF getColorAtCursor(void) {
POINT p; COLORREF color; HDC hDC; BOOL b;
/* Get the device context for the screen */ hDC = GetDC(NULL); if (hDC == NULL) return CLR_INVALID;
/* Get the current cursor position */ b = GetCursorPos(&p); if (!b) return CLR_INVALID;
/* Retrieve the color at that position */ color = GetPixel(hDC, p.x, p.y);
/* Release the device context again */ ReleaseDC(GetDesktopWindow(), hDC);
return color;
}</lang>
C#
<lang csharp>using System; using System.Drawing; using System.Windows.Forms;
class Program {
static Color GetPixel(Point position) { using (var bitmap = new Bitmap(1, 1)) { using (var graphics = Graphics.FromImage(bitmap)) { graphics.CopyFromScreen(position, new Point(0, 0), new Size(1, 1)); } return bitmap.GetPixel(0, 0); } }
static void Main() { Console.WriteLine(GetPixel(Cursor.Position)); }
}</lang> Sample output: <lang>Color [A=255, R=243, G=242, B=231]</lang>
Clojure
<lang lisp>(defn get-color-at [x y]
(.getPixelColor (java.awt.Robot.) x y))</lang>
Delphi
<lang Delphi> program ScreenPixel;
{$APPTYPE CONSOLE}
uses
Windows, SysUtils, Graphics;
// Use this function in a GUI application to return the color
function GetPixelColourAsColor(const PixelCoords: TPoint): TColor;
var
dc: HDC;
begin
// Get Device Context of windows desktop dc := GetDC(0); // Read the color of the pixel at the given coordinates Result := GetPixel(dc,PixelCoords.X,PixelCoords.Y);
end;
// Use this function to get a string representation of the current colour function GetPixelColourAsString(const PixelCoords: TPoint): string; var
r,g,b: Byte; col: TColor;
begin
col := GetPixelColourAsColor(PixelCoords);
// Convert the Delphi TColor value to it's RGB components r := col and $FF; g := (col shr 8) and $FF; b := (col shr 16) and $FF;
// Format the result Result := 'R('+IntToStr(r)+') G('+IntToStr(g)+') G('+IntToStr(b)+')';
{ Alternatively, format the result as follows to get a string representation of the Delphi TColor value
Result := ColorToString(GetPixel(dc,curP.X,curP.Y)); }
end;
var
s: string; P: TPoint;
begin
s := ;
Writeln('Move mouse over a pixel. Hit return to get colour of selected pixel.');
repeat Readln(s); if s = then begin GetCursorPos(P); Writeln('Colour at cursor position X:'+ IntToStr(P.X)+' Y:'+ IntToStr(P.Y) +' = '+ GetPixelColourAsString(P) ); Writeln(); Writeln('Move mouse and hit enter again.'); end; until SameText(s,'quit');
end. </lang>
Example output:
Move mouse over a pixel. Hit return to get colour of selected pixel. Colour at cursor position X:429 Y:161 = R(0) G(0) B(0) Move mouse and hit enter again. Colour at cursor position X:942 Y:358 = R(182) G(206) B(231) Move mouse and hit enter again. Colour at cursor position X:704 Y:103 = R(240) G(240) B(240) Move mouse and hit enter again. Colour at cursor position X:2756 Y:59 = R(250) G(196) B(182)
F#
<lang fsharp>open System.Drawing open System.Windows.Forms
let GetPixel x y =
use img = new Bitmap(1,1) use g = Graphics.FromImage(img) g.CopyFromScreen(new Point(x,y), new Point(0,0), new Size(1,1)) let clr = img.GetPixel(0,0) (clr.R, clr.G, clr.B)
let GetPixelAtMouse () =
let pt = Cursor.Position GetPixel pt.X pt.Y</lang>
C++/CLI
Pixel's color from cursor position: <lang cpp> POINT pt; pt.X=Cursor->Position.X; pt.Y=Cursor->Position.Y; Bitmap ^ myBitmap = gcnew Bitmap(1,1); Graphics ^ g = Graphics::FromImage(myBitmap); g->CopyFromScreen(pt, Drawing::Point(0, 0), Drawing::Size(1, 1)); Color color = myBitmap->GetPixel(0,0); this->Red->Text=color.R.ToString(); this->Blue->Text=color.B.ToString(); this->Green->Text=color.G.ToString(); </lang>
Integer BASIC
See Applesoft BASIC.
Java
<lang java>public static Color getColorAt(int x, int y){
return new Robot().getPixelColor(x, y);
}</lang>
Liberty BASIC
<lang lb>'This example requires the Windows API Struct point, x As long, y As long
hDC = GetDC(0) result = GetCursorPos() Print GetPixel(hDC, point.x.struct, point.y.struct) Call ReleaseDC 0, hDC End
Sub ReleaseDC hWnd, hDC CallDLL #user32,"ReleaseDC", hWnd As uLong, hDC As uLong, ret As Long End Sub
Function GetDC(hWnd) CallDLL #user32, "GetDC", hWnd As uLong, GetDC As uLong End Function
Function GetCursorPos() CallDLL #user32, "GetCursorPos", point As struct, GetCursorPos As uLong End Function
Function GetPixel(hDC, x, y) CallDLL #gdi32, "GetPixel", hDC As uLong, x As long, y As long, GetPixel As long End Function</lang>
Locomotive Basic
<lang locobasic>10 x=320:y=200 20 color=TEST(x,y) 30 PRINT "Pen color at"; x; y; "is"; color</lang>
Logo
CLEARSCREEN SHOW PIXEL [255 255 255]
PHP
<lang php>$img = imagegrabscreen(); $color = imagecolorat($im, 10, 50); imagedestroy($im);</lang>
PicoLisp
Using 'grabc' as recommended in the C solution <lang PicoLisp>(in '(grabc)
(mapcar hex (cdr (line NIL 1 2 2 2))) )</lang>
Output:
73,61,205 -> (73 61 205)
PureBasic
Return the color used at the x,y position in the current output. If the current output has an alpha channel then the result will be a 32bit RGBA value, otherwise it will be a 24bit RGB value. The color can be split in their RGB and alpha values by using the Red(), Green(), Blue() and Alpha() functions.
<lang PureBasic>Color = Point(x, y)</lang>
To get the colour of a pixel on the screen when it is not managed by PureBasic (ie. from other programs' windows), it is necessary to use Windows API. This works only under Windows. <lang PureBasic> hDC = GetDC_(0) Color = GetPixel_(hDC, x, y) ReleaseDC_(0, hDC)</lang>
This work fine!!
<lang PureBasic>poz.point If OpenWindow(0,0,0,100,45,"Get pixel color at cursor position",#PB_Window_MinimizeGadget)
TextGadget(0,0,0,50,12,"Red: ") TextGadget(1,0,15,50,12,"Green: ") TextGadget(2,0,30,50,12,"Blue: ") TextGadget(3,50,0,50,12,"") TextGadget(4,50,15,50,12,"") TextGadget(5,50,30,50,12,"") hDC = GetDC_(0) Repeat oldx=poz\x oldy=poz\y
GetCursorPos_(@poz) Color = GetPixel_(hDC, poz\x, poz\y) If poz\x<>oldx Or poz\y<>oldy
SetGadgetText(3,Str(Red(color))) SetGadgetText(4,Str(Green(color))) SetGadgetText(5,Str(Blue(color)))
EndIf event=WaitWindowEvent(200) Until event=#PB_Event_CloseWindow ReleaseDC_(0, hDC) EndIf</lang>
Python
<lang python>def get_pixel_colour(i_x, i_y): import win32gui i_desktop_window_id = win32gui.GetDesktopWindow() i_desktop_window_dc = win32gui.GetWindowDC(i_desktop_window_id) long_colour = win32gui.GetPixel(i_desktop_window_dc, i_x, i_y) i_colour = int(long_colour) return (i_colour & 0xff), ((i_colour >> 8) & 0xff), ((i_colour >> 16) & 0xff)
print get_pixel_colour(0, 0)</lang>
only
<lang python>def get_pixel_colour(i_x, i_y): import PIL.ImageGrab return PIL.ImageGrab.grab().load()[i_x, i_y]
print get_pixel_colour(0, 0)</lang>
<lang python>def get_pixel_colour(i_x, i_y): import PIL.Image # python-imaging import PIL.ImageStat # python-imaging import Xlib.display # python-xlib o_x_root = Xlib.display.Display().screen().root o_x_image = o_x_root.get_image(i_x, i_y, 1, 1, Xlib.X.ZPixmap, 0xffffffff) o_pil_image_rgb = PIL.Image.fromstring("RGB", (1, 1), o_x_image.data, "raw", "BGRX") lf_colour = PIL.ImageStat.Stat(o_pil_image_rgb).mean return tuple(map(int, lf_colour))
print get_pixel_colour(0, 0)</lang>
<lang python>def get_pixel_colour(i_x, i_y): import gtk # python-gtk2 o_gdk_pixbuf = gtk.gdk.Pixbuf(gtk.gdk.COLORSPACE_RGB, False, 8, 1, 1) o_gdk_pixbuf.get_from_drawable(gtk.gdk.get_default_root_window(), gtk.gdk.colormap_get_system(), i_x, i_y, 0, 0, 1, 1) return tuple(o_gdk_pixbuf.get_pixels_array().tolist()[0][0])
print get_pixel_colour(0, 0)</lang>
<lang python>def get_pixel_colour(i_x, i_y): import PyQt4.QtGui # python-qt4 app = PyQt4.QtGui.QApplication([]) long_qdesktop_id = PyQt4.QtGui.QApplication.desktop().winId() long_colour = PyQt4.QtGui.QPixmap.grabWindow(long_qdesktop_id).toImage().pixel(i_x, i_y) i_colour = int(long_colour) return ((i_colour >> 16) & 0xff), ((i_colour >> 8) & 0xff), (i_colour & 0xff)
print get_pixel_colour(0, 0)</lang>
Tcl
Works only on X11 or OSX with Xquartz. <lang tcl>package require Tcl 8.5 package require Tk
- Farm out grabbing the screen to an external program.
- If it was just for a Tk window, we'd use the tkimg library instead
proc grabScreen {image} {
set pipe [open {|xwd -root -silent | convert xwd:- ppm:-} rb] $image put [read $pipe] close $pipe
}
- Get the RGB data for a particular pixel (global coords)
proc getPixelAtPoint {x y} {
set buffer [image create photo] grabScreen $buffer set data [$image get $x $y] image delete $buffer return $data
}
- Demo...
puts [format "pixel at mouse: (%d,%d,%d)" \
{*}[getPixelAtPoint {*}[winfo pointerxy .]]]</lang>
TI-89 BASIC
Only the graph screen can be read.
<lang ti89b>pxlTest(y, x) © returns boolean</lang>
Visual Basic .NET
<lang vbnet> Private Function GetPixelColor(ByVal Location As Point) As Color
Dim b As New Bitmap(1, 1) Dim g As Graphics = Graphics.FromImage(b)
g.CopyFromScreen(Location, Point.Empty, New Size(1, 1))
Return b.GetPixel(0, 0)
End Function</lang>
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