pngimage.java

处理PDF

    void decodePass( int xOffset, int yOffset,
    int xStep, int yStep,
    int passWidth, int passHeight) {
        if ((passWidth == 0) || (passHeight == 0)) {
            return;
        }
        
        int bytesPerRow = (inputBands*passWidth*bitDepth + 7)/8;
        byte[] curr = new byte[bytesPerRow];
        byte[] prior = new byte[bytesPerRow];
        
        // Decode the (sub)image row-by-row
        int srcY, dstY;
        for (srcY = 0, dstY = yOffset;
        srcY < passHeight;
        srcY++, dstY += yStep) {
            // Read the filter type byte and a row of data
            int filter = 0;
            try {
                filter = dataStream.read();
                dataStream.readFully(curr, 0, bytesPerRow);
            } catch (Exception e) {
                // empty on purpose
            }
            
            switch (filter) {
                case PNG_FILTER_NONE:
                    break;
                case PNG_FILTER_SUB:
                    decodeSubFilter(curr, bytesPerRow, bytesPerPixel);
                    break;
                case PNG_FILTER_UP:
                    decodeUpFilter(curr, prior, bytesPerRow);
                    break;
                case PNG_FILTER_AVERAGE:
                    decodeAverageFilter(curr, prior, bytesPerRow, bytesPerPixel);
                    break;
                case PNG_FILTER_PAETH:
                    decodePaethFilter(curr, prior, bytesPerRow, bytesPerPixel);
                    break;
                default:
                    // Error -- uknown filter type
                    throw new RuntimeException("PNG filter unknown.");
            }
            
            processPixels(curr, xOffset, xStep, dstY, passWidth);
            
            // Swap curr and prior
            byte[] tmp = prior;
            prior = curr;
            curr = tmp;
        }
    }
    
    void processPixels(byte curr[], int xOffset, int step, int y, int width) {
        int srcX, dstX;

        int out[] = getPixel(curr);
        int sizes = 0;
        switch (colorType) {
            case 0:
            case 3:
            case 4:
                sizes = 1;
                break;
            case 2:
            case 6:
                sizes = 3;
                break;
        }
        if (image != null) {
            dstX = xOffset;
            int yStride = (sizes*this.width*(bitDepth == 16 ? 8 : bitDepth)+ 7)/8;
            for (srcX = 0; srcX < width; srcX++) {
                setPixel(image, out, inputBands * srcX, sizes, dstX, y, bitDepth, yStride);
                dstX += step;
            }
        }
        if (palShades) {
            if ((colorType & 4) != 0) {
                if (bitDepth == 16) {
                    for (int k = 0; k < width; ++k)
                        out[k * inputBands + sizes] >>>= 8;
                }
                int yStride = this.width;
                dstX = xOffset;
                for (srcX = 0; srcX < width; srcX++) {
                    setPixel(smask, out, inputBands * srcX + sizes, 1, dstX, y, 8, yStride);
                    dstX += step;
                }
            }
            else { //colorType 3
                int yStride = this.width;
                int v[] = new int[1];
                dstX = xOffset;
                for (srcX = 0; srcX < width; srcX++) {
                    int idx = out[srcX];
                    if (idx < trans.length)
                        v[0] = trans[idx];
                    setPixel(smask, v, 0, 1, dstX, y, 8, yStride);
                    dstX += step;
                }
            }
        }
        else if (genBWMask) {
            switch (colorType) {
                case 3: {
                    int yStride = (this.width + 7) / 8;
                    int v[] = new int[1];
                    dstX = xOffset;
                    for (srcX = 0; srcX < width; srcX++) {
                        int idx = out[srcX];
                        if (idx < trans.length)
                            v[0] = (trans[idx] == 0 ? 1 : 0);
                        setPixel(smask, v, 0, 1, dstX, y, 1, yStride);
                        dstX += step;
                    }
                    break;
                }
                case 0: {
                    int yStride = (this.width + 7) / 8;
                    int v[] = new int[1];
                    dstX = xOffset;
                    for (srcX = 0; srcX < width; srcX++) {
                        int g = out[srcX];
                        v[0] = (g == transRedGray ? 1 : 0);
                        setPixel(smask, v, 0, 1, dstX, y, 1, yStride);
                        dstX += step;
                    }
                    break;
                }
                case 2: {
                    int yStride = (this.width + 7) / 8;
                    int v[] = new int[1];
                    dstX = xOffset;
                    for (srcX = 0; srcX < width; srcX++) {
                        int markRed = inputBands * srcX;
                        v[0] = (out[markRed] == transRedGray && out[markRed + 1] == transGreen 
                            && out[markRed + 2] == transBlue ? 1 : 0);
                        setPixel(smask, v, 0, 1, dstX, y, 1, yStride);
                        dstX += step;
                    }
                    break;
                }
            }
        }
    }
    
    static int getPixel(byte image[], int x, int y, int bitDepth, int bytesPerRow) {
        if (bitDepth == 8) {
            int pos = bytesPerRow * y + x;
            return image[pos] & 0xff;
        }
        else {
            int pos = bytesPerRow * y + x / (8 / bitDepth);
            int v = image[pos] >> (8 - bitDepth * (x % (8 / bitDepth))- bitDepth);
            return v & ((1 << bitDepth) - 1);
        }
    }
    
    static void setPixel(byte image[], int data[], int offset, int size, int x, int y, int bitDepth, int bytesPerRow) {
        if (bitDepth == 8) {
            int pos = bytesPerRow * y + size * x;
            for (int k = 0; k < size; ++k)
                image[pos + k] = (byte)data[k + offset];
        }
        else if (bitDepth == 16) {
            int pos = bytesPerRow * y + size * x;
            for (int k = 0; k < size; ++k)
                image[pos + k] = (byte)(data[k + offset] >>> 8);
        }
        else {
            int pos = bytesPerRow * y + x / (8 / bitDepth);
            int v = data[offset] << (8 - bitDepth * (x % (8 / bitDepth))- bitDepth);
            image[pos] |= v;
        }
    }
    
    int[] getPixel(byte curr[]) {
        switch (bitDepth) {
            case 8: {
                int out[] = new int[curr.length];
                for (int k = 0; k < out.length; ++k)
                    out[k] = curr[k] & 0xff;
                return out;
            }
            case 16: {
                int out[] = new int[curr.length / 2];
                for (int k = 0; k < out.length; ++k)
                    out[k] = ((curr[k * 2] & 0xff) << 8) + (curr[k * 2 + 1] & 0xff);
                return out;
            }
            default: {
                int out[] = new int[curr.length * 8 / bitDepth];
                int idx = 0;
                int passes = 8 / bitDepth;
                int mask = (1 << bitDepth) - 1;
                for (int k = 0; k < curr.length; ++k) {
                    for (int j = passes - 1; j >= 0; --j) {
                        out[idx++] = (curr[k] >>> (bitDepth * j)) & mask; 
                    }
                }
                return out;
            }
        }
    }
    
    private static void decodeSubFilter(byte[] curr, int count, int bpp) {
        for (int i = bpp; i < count; i++) {
            int val;
            
            val = curr[i] & 0xff;
            val += curr[i - bpp] & 0xff;
            
            curr[i] = (byte)val;
        }
    }
    
    private static void decodeUpFilter(byte[] curr, byte[] prev,
    int count) {
        for (int i = 0; i < count; i++) {
            int raw = curr[i] & 0xff;
            int prior = prev[i] & 0xff;
            
            curr[i] = (byte)(raw + prior);
        }
    }
    
    private static void decodeAverageFilter(byte[] curr, byte[] prev,
    int count, int bpp) {
        int raw, priorPixel, priorRow;
        
        for (int i = 0; i < bpp; i++) {
            raw = curr[i] & 0xff;
            priorRow = prev[i] & 0xff;
            
            curr[i] = (byte)(raw + priorRow/2);
        }
        
        for (int i = bpp; i < count; i++) {
            raw = curr[i] & 0xff;
            priorPixel = curr[i - bpp] & 0xff;
            priorRow = prev[i] & 0xff;
            
            curr[i] = (byte)(raw + (priorPixel + priorRow)/2);
        }
    }
    
    private static int paethPredictor(int a, int b, int c) {
        int p = a + b - c;
        int pa = Math.abs(p - a);
        int pb = Math.abs(p - b);
        int pc = Math.abs(p - c);
        
        if ((pa <= pb) && (pa <= pc)) {
            return a;
        } else if (pb <= pc) {
            return b;
        } else {
            return c;
        }
    }
    
    private static void decodePaethFilter(byte[] curr, byte[] prev,
    int count, int bpp) {
        int raw, priorPixel, priorRow, priorRowPixel;
        
        for (int i = 0; i < bpp; i++) {
            raw = curr[i] & 0xff;
            priorRow = prev[i] & 0xff;
            
            curr[i] = (byte)(raw + priorRow);
        }
        
        for (int i = bpp; i < count; i++) {
            raw = curr[i] & 0xff;
            priorPixel = curr[i - bpp] & 0xff;
            priorRow = prev[i] & 0xff;
            priorRowPixel = prev[i - bpp] & 0xff;
            
            curr[i] = (byte)(raw + paethPredictor(priorPixel,
            priorRow,
            priorRowPixel));
        }
    }
    
    static class NewByteArrayOutputStream extends ByteArrayOutputStream {
        public byte[] getBuf() {
            return buf;
        }
    }

/**
 * Gets an <CODE>int</CODE> from an <CODE>InputStream</CODE>.
 *
 * @param		is      an <CODE>InputStream</CODE>
 * @return		the value of an <CODE>int</CODE>
 */
    
    public static final int getInt(InputStream is) throws IOException {
        return (is.read() << 24) + (is.read() << 16) + (is.read() << 8) + is.read();
    }
    
/**
 * Gets a <CODE>word</CODE> from an <CODE>InputStream</CODE>.
 *
 * @param		is      an <CODE>InputStream</CODE>
 * @return		the value of an <CODE>int</CODE>
 */
    
    public static final int getWord(InputStream is) throws IOException {
        return (is.read() << 8) + is.read();
    }
    
/**
 * Gets a <CODE>String</CODE> from an <CODE>InputStream</CODE>.
 *
 * @param		is      an <CODE>InputStream</CODE>
 * @return		the value of an <CODE>int</CODE>
 */
    
    public static final String getString(InputStream is) throws IOException {
        StringBuffer buf = new StringBuffer();
        for (int i = 0; i < 4; i++) {
            buf.append((char)is.read());
        }
        return buf.toString();
    }

}