core/SkBlitter_A1.cpp

/*
 * Copyright 2006 The Android Open Source Project
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */


#include "SkCoreBlitters.h"

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

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;
    }
}