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--- part_8-_editing_the_pixels_array [2007/08/30 13:53]
127.0.0.1 external edit
+++ part_8-_editing_the_pixels_array [2007/09/13 07:27] (current)
scarl Fixed misunderstanding colors as objects, not ints
@@ Line 2: / Line 2: @@
 === Part 8: Editing the pixels[] array ===
-When using the global pixels[] array:
+''pixels[]'' holds a color value for every pixel currently drawn in the system display window.  It can be read and modified to change the display.  To use this array to modify the display:
-  * You have to call ''loadPixels()'' to populate the array (otherwise it will be null).
+  * First call ''loadPixels()'' to populate the array (otherwise it will be null).
-  * You can access and change the array directly.
+  * Now you can access and change the array directly.
-  * When you have finished editing, you have to call ''updatePixels()'' to commit the changes. This will redraw the screen.
+  * When finished editing, call ''updatePixels()'' to commit the changes. This will redraw the screen.
-The global ''pixels[]'' array contains every pixel in the window in the form of color objects.
+//By default//, the color values stored in ''pixels[]'' are made up of Red, Green and Blue (RGB) values.  This is called RGB mode.  Each of the Red, Green, and Blue values are 8-bit numbers from 0 to 255:
-A color object is made or Red, Green and Blue (RGB) values, which go from 0 to 255:
   color c = color(125,125,125);
 You can read these values back with the red(), green() and blue() functions. To modify a pixel, you would use something like:
   pixels[x] = color(125, green(pixels[x]), blue(pixels[x]));
+Note:  a common error is to treat a color value as an object.   Color values are just 32-bit integers (8 bits for each RGB value plus alpha channel information stored in the extra 8 bits - we'll talk about alpha channels later on), so any code which treats a color as an object will cause a syntax error.  Treat color values as the type color in Processing code, and as type ''int'' in Java code.
 \\
-Next: [[Part 9- A Few Functions for Creating and Manipulating Basic Shapes]]
-Last: [[Part 7- A Few Useful Global Variables]]
+Prev: [[Part 7- A Few Useful Global Variables]] | Next: [[Part 9- A Few Functions for Creating and Manipulating Basic Shapes]]

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