include/graphics/SkMask.h

/* include/graphics/SkMask.h
**
** Copyright 2006, Google Inc.
**
** Licensed under the Apache License, Version 2.0 (the "License"); 
** you may not use this file except in compliance with the License. 
** You may obtain a copy of the License at 
**
**     http://www.apache.org/licenses/LICENSE-2.0 
**
** Unless required by applicable law or agreed to in writing, software 
** distributed under the License is distributed on an "AS IS" BASIS, 
** WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 
** See the License for the specific language governing permissions and 
** limitations under the License.
*/

#ifndef SkMask_DEFINED
#define SkMask_DEFINED

#include "SkRect.h"

/** \class SkMask
    SkMask is used to describe alpha bitmaps, either 1bit, 8bit, or
    the 3-channel 3D format. These are passed to SkMaskFilter objects.
*/
struct SkMask {
    enum Format {
        kBW_Format, //!< 1bit per pixel mask (e.g. monochrome)
        kA8_Format, //!< 8bits per pixel mask (e.g. antialiasing)
        k3D_Format, //!< 3 8bit per pixl planes: alpha, mul, add
        kLCD_Format //!< 3 bytes/pixel: r/g/b
    };

    uint8_t*    fImage;
    SkRect16    fBounds;
    uint16_t    fRowBytes;
    uint8_t     fFormat;    // Format

    /** Return the byte size of the mask, assuming only 1 plane.
        Does not account for k3D_Format. For that, use computeFormatImageSize()
    */
    size_t computeImageSize() const;
    /** Return the byte size of the mask, taking into account
        any extra planes (e.g. k3D_Format).
    */
    size_t computeTotalImageSize() const;

    /** Returns the address of the byte that holds the specified bit.
        Asserts that the mask is kBW_Format, and that x,y are in range.
        x,y are in the same coordiate space as fBounds.
    */
    uint8_t* getAddr1(int x, int y) const
    {
        SkASSERT(fFormat == kBW_Format);
        SkASSERT(fBounds.contains(x, y));
        SkASSERT(fImage != nil);
        return fImage + ((x - fBounds.fLeft) >> 3) + (y - fBounds.fTop) * fRowBytes;
    }
    /** Returns the address of the specified byte.
        Asserts that the mask is kA8_Format, and that x,y are in range.
        x,y are in the same coordiate space as fBounds.
    */
    uint8_t* getAddr(int x, int y) const
    {
        SkASSERT(fFormat != kBW_Format);
        SkASSERT(fBounds.contains(x, y));
        SkASSERT(fImage != nil);
        return fImage + x - fBounds.fLeft + (y - fBounds.fTop) * fRowBytes;
    }

    static uint8_t* AllocImage(size_t bytes);
    static void FreeImage(uint8_t* image);
    
    enum CreateMode {
        kJustComputeBounds_CreateMode,      //!< compute bounds and return
        kJustRenderImage_CreateMode,        //!< render into preallocate mask
        kComputeBoundsAndRenderImage_CreateMode  //!< compute bounds, alloc image and render into it
    };
};

#endif