libsgl/sgl/SkBlitter_A1.cpp

/* libs/graphics/sgl/SkBlitter_A1.cpp
**
** Copyright 2006, The Android Open Source Project
**
** 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.
*/

#include "SkCoreBlitters.h"

SkA1_Blitter::SkA1_Blitter(const SkBitmap& device, const SkPaint& paint)
    : INHERITED(device)
{
    fSrcA = SkToU8(SkColorGetA(paint.getColor()));
}

void SkA1_Blitter::blitH(int x, int y, int width)
{
    SkASSERT(x >= 0 && y >= 0 && (unsigned)(x + width) <= (unsigned)fDevice.width());

    if (fSrcA <= 0x7F)
        return;

    uint8_t* dst = fDevice.getAddr1(x, y);
    int right = x + width;

    int left_mask = 0xFF >> (x & 7);
    int rite_mask = 0xFF << (8 - (right & 7));
    int full_runs = (right >> 3) - ((x + 7) >> 3);

    // check for empty right mask, so we don't read off the end (or go slower than we need to)
    if (rite_mask == 0)
    {
        SkASSERT(full_runs >= 0);
        full_runs -= 1;
        rite_mask = 0xFF;
    }
    if (left_mask == 0xFF)
        full_runs -= 1;

    if (full_runs < 0)
    {
        SkASSERT((left_mask & rite_mask) != 0);
        *dst |= (left_mask & rite_mask);
    }
    else
    {
        *dst++ |= left_mask;
        memset(dst, 0xFF, full_runs);
        dst += full_runs;
        *dst |= rite_mask;
    }
}