As stated in Flash Actionscript Contest: erase tool you can not "erase" a particular area of a Sprite, MovieClip, and Shape on which were traced lines or rectangles using the pointer graphics. There is, in fact, the only method clear() which, however, has no effect on the whole area of our object. The solution to the problem lies in the possibility of using the Bitmap and BitmapData objects. As we shall see we can access and manipulate bitmap data directly in order to "erase" the traits with a real instrument "eraser."

I will present two different methods for achieving the "gate". The first "draw" (delete) data directly into BitmapData, using the method fillRect() - you can also use setPixel() for example. The second method, the preferred one, uses the methods of mergers (blendMode).

First of all let's see what kind of organization is needed to achieve a minimal simple Painter in Flash. The outline presented below applies to both proposals of the "gate"

I created three layers: the first, MovieClip or Sprite, works as a manager and background events (MouseDown, MouseMove and MouseUp). The second, the bitmap is our main layer, the one that will contain the graphics actually designed and which will apply the "delete". The third and final layer, the Shape, addresses two issues: the first is being able to directly use the functions provided by the graphics pointer (as lineStyle drawRect() etc. ...). It also increases performance during tracking chart, as detailed below.

Method 1 - Direct access to bitmap data

This "sample" uses the method fillRect() directly on BitmapData (layer 2) after the design has been copied (using the method draw() from the Shape (layer 3) to Bitmap (layer 2).

To understand how it works here is the same movie with layers and disordered in pseudo 3D - drawn in colored box - source:

As you can see you draw on layer 3, the Shape. MouseUp event fires when the content is copied on the Shape Bitmap (and therefore the data are present in BitmapData) and then the Shape is clean clear()

Note: this last point, the clear() the Shape, not be underestimated. Some examples of the painter in Flash (almost all devoid of a true "gate") by drawing directly on a MovieClip or Shape, keeping the data on that draw. After a little 'you draw the system slows down, as the area "vector" of the MovieClip increases. In the method I have presented this problem is solved because the data vector of Shape, when they are copied to the Bitmap, tasformati are in bits and Shape is deleted, freeing up memory and return it to the design flow!

Holding down the Ctrl (control) is "deleted" directly via the BitmapData fillRect() This is possible because fillRect() like other methods that operate on a BitmapData, allow you to set the "color" through 0xARGB, where A is the alpha value, transparent.

The code is as follows - source:

Line 61, as shown in the code above, it runs so long when the Control key is pressed. As you can see this section of code draws directly into the BitmapData with color 0, which is 0x0000!

METHOD 2 - Using Blending Modes

This is probably the best method to time lets you use any kind of "gate". Unlike the previous method does not directly access the bitmap data present in BitmapData, but exploit the blend (blendMode) and the copy of bitmaps using the method draw().

3D version - source:

Exactly the same way that we copy the data from the Bitmap Shape, the "gate" is "simultaneously" by copying the data from the Shape Bitmap but this time, setting the blendMode method draw() to erase

The code is as follows - source:

This code is not very dissimilar from the previous year. The real difference is in row 52! This determines the "blend mode" when you copy from the Shape Bitmap, and when the Control key is pressed is used the method of fusion erase
That's all! We talk more about the bitmap as soon as possible and the differences between MovieClip, Sprite, Shape and Bitmap ... All visual objects!

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