* Added an 'eyedropper' tool in the colour picker. With the colour picker open,

you can click on the 'Sample' button, to sample any colour on the Blender
screen. This is really useful in the compositor, and would probably be good for
sampling footage in any eventual chroma key nodes that may be made, too.

LMB to pick the colour, ESC or RMB to cancel.

source/blender/include/BIF_resources.h

@@ -233,7 +233,7 @@ typedef enum {
 	ICON_IPO_DEHLT,
 	ICON_LIBRARY_DEHLT,
 	ICON_IMAGE_DEHLT,
-	ICON_WINDOW_FULLSCREEN,
+	ICON_EYEDROPPER,
 	ICON_WINDOW_WINDOW,
 	ICON_PANEL_CLOSE,
 	

source/blender/src/interface.c

@@ -80,6 +80,7 @@
 #include "BKE_texture.h"
 #include "BKE_utildefines.h"
 
+#include "BIF_cursors.h"
 #include "BIF_gl.h"
 #include "BIF_graphics.h"
 #include "BIF_keyval.h"
@@ -101,6 +102,7 @@
 #include "mydevice.h"
 #include "interface.h"
 #include "blendef.h"
+#include "winlay.h"
 
 /* naming conventions:
  * 
@@ -3040,9 +3042,78 @@ static void do_palette_hex_cb(void *bt1, void *hexcl)
 	
 	but= but1->block->buttons.first;
 	ui_block_flush_back(but->block);
-
 }
 
+
+/* used for both 3d view and image window */
+static void do_palette_sample_cb(void *bt1, void *col1)	/* frontbuf */
+{
+	uiBut *but1= (uiBut *)bt1;
+	uiBut *but;
+	float *col= (float *)col1;
+	float tempcol;
+	int x=0, y=0;
+	short mval[2];
+	float hsv[3];
+	short capturing;
+	int oldcursor;
+	Window *win;
+	unsigned short dev;
+	
+	oldcursor=get_cursor();
+	win=winlay_get_active_window();
+	
+	while (get_mbut() & L_MOUSE) BIF_wait_for_statechange();
+	
+	SetBlenderCursor(BC_CROSSCURSOR);
+	
+	/* loop and wait for a mouse click */
+	capturing = TRUE;
+	while(capturing) {
+		char ascii;
+		short val;
+		
+		dev = extern_qread_ext(&val, &ascii);
+		
+		if(dev==INPUTCHANGE) break;
+		if(get_mbut() & R_MOUSE) break;
+		else if(get_mbut() & L_MOUSE) {
+			uiGetMouse(mywinget(), mval);
+			x= mval[0]; y= mval[1];
+			
+			capturing = FALSE;
+			break;
+		}
+		else if(dev==ESCKEY) break;
+	}
+	window_set_cursor(win, oldcursor);
+	
+	if(capturing) return;
+	
+	if(x<0 || y<0) return;
+	
+	/* if we've got a glick, use OpenGL to sample the colour under the mouse pointer */
+	glReadBuffer(GL_FRONT);
+	glReadPixels(x, y, 1, 1, GL_RGBA, GL_FLOAT, &tempcol);
+	glReadBuffer(GL_BACK);
+	
+	col = (float *)&tempcol;
+	
+	/* and send that colour back to the picker */
+	rgb_to_hsv(col[0], col[1], col[2], hsv, hsv+1, hsv+2);
+	update_picker_buts_hsv(but1->block, hsv, but1->poin);
+	update_picker_hex(but1->block, col);
+	
+	for (but= but1->block->buttons.first; but; but= but->next) {
+		ui_check_but(but);
+		ui_draw_but(but);
+	}
+	
+	but= but1->block->buttons.first;
+	ui_block_flush_back(but->block);
+}
+
+
 /* color picker, Gimp version. mode: 'f' = floating panel, 'p' =  popup */
 /* col = read/write to, hsv/old/hexcol = memory for temporal use */
 void uiBlockPickerButtons(uiBlock *block, float *col, float *hsv, float *old, char *hexcol, char mode, short retval)
@@ -3050,7 +3121,6 @@ void uiBlockPickerButtons(uiBlock *block, float *col, float *hsv, float *old, ch
 	uiBut *bt;
 	float h, offs;
 	int a;
-	
 
 	VECCOPY(old, col);	// old color stored there, for palette_cb to work
 	
@@ -3087,6 +3157,10 @@ void uiBlockPickerButtons(uiBlock *block, float *col, float *hsv, float *old, ch
 
 	offs= FPICK+2*DPICK+BPICK;
 
+	bt= uiDefIconTextBut(block, BUT, UI_RETURN_OK, ICON_EYEDROPPER, "Sample", offs+55, 170, 85, 20, 0, 0, 0, 0, 0, "Sample the color underneath the following mouse click (ESC or RMB to cancel)");
+	uiButSetFunc(bt, do_palette_sample_cb, bt, col);
+	uiButSetFlag(bt, UI_TEXT_LEFT);
+	
 	bt= uiDefBut(block, TEX, retval, "Hex: ", offs, 140, 140, 20, hexcol, 0, 8, 0, 0, "Hex triplet for colour (#RRGGBB)");
 	uiButSetFunc(bt, do_palette_hex_cb, bt, hexcol);
 
@@ -3108,7 +3182,6 @@ void uiBlockPickerButtons(uiBlock *block, float *col, float *hsv, float *old, ch
 	uiBlockEndAlign(block);
 }
 
-
 static int ui_do_but_COL(uiBut *but)
 {
 	uiBlock *block;