Color of a screen pixel

From Rosetta Code

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.

Contents 1 AutoHotkey 2 BASIC 3 C 4 C# 5 Clojure 6 F# 7 Java 8 PureBasic 9 Python 10 Tcl 11 TI-89 BASIC

[edit] AutoHotkey

MouseGetPos, MouseX, MouseY
PixelGetColor, color, %MouseX%, %MouseY%

[edit] BASIC

Works with: QuickBasic version 4.5

In a graphics mode (for instance, SCREEN 13 or SCREEN 12)

color = POINT(x, y)

[edit] C

Works with: Windows

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;
}

[edit] C#

using System;
using System.Drawing;
using System.Windows.Forms;
 
Bitmap img = new Bitmap(1, 1);
Graphics g = Graphics.FromImage(img);
g.CopyFromScreen(new Point(x, y), new Point(0, 0), new Size(1, 1));
 
Color color = img.GetPixel(x, y);

[edit] Clojure

(defn get-color-at [x y]
  (.getPixelColor (java.awt.Robot.) x y))

[edit] F#

The C# example copies the entire screen into our private bitmap but that's unnecessary. All we need is the single pixel. Also, it doesn't appear that the bitmap and graphics object are being disposed of there. Other than that, this is essentially identical to that solution.

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 
 

[edit] Java

public static Color getColorAt(int x, int y){
   return new Robot().getPixelColor(x, y);
}

[edit] 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.

Color = Point(x, y)

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.

 
hDC = GetDC_(0)
Color = GetPixel_(hDC, x, y)
ReleaseDC_(0, hDC)

This work fine!!

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

[edit] Python

Library: PyWin32

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)

Library: PIL

Works with: Windows only

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)

Library: PIL Library: python-xlib

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)

Library: PyGTK

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)

Library: PyQt

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)

[edit] Tcl

Library: Tk Works only on X11 or OSX with Xquartz.

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 .]]]

[edit] TI-89 BASIC

Only the graph screen can be read.

pxlTest(y, x)              © returns boolean