using Selenium.Internal;

using System;

using System.Drawing;

using System.Drawing.Imaging;

using System.IO;

namespace Selenium.Pdf {

static class PdfImage {

private static long ENCODER_JPEG_QUALITY = 80L;

private static readonly ImageCodecInfo ENCODER_PNG;

private static readonly ImageCodecInfo ENCODER_JPEG;

private static readonly EncoderParameters ENCODER_JPEG_PARAMS;

static PdfImage() {

//Cache the JPEG and PNG GDI+ encoders

Guid guidPng = ImageFormat.Png.Guid;

Guid guidJpeg = ImageFormat.Jpeg.Guid;

foreach (ImageCodecInfo codec in ImageCodecInfo.GetImageDecoders()) {

if (codec.FormatID == guidJpeg) {

ENCODER_JPEG = codec;

} else if (codec.FormatID == guidPng) {

ENCODER_PNG = codec;

}

}

//Set the JPEG encoder Quality

ENCODER_JPEG_PARAMS = new EncoderParameters(1);

ENCODER_JPEG_PARAMS.Param[0] = new EncoderParameter(

System.Drawing.Imaging.Encoder.Quality, ENCODER_JPEG_QUALITY);

}

/// <summary>

/// Encodes a bitmap to JPEG to a stream and returns the writen length.

/// </summary>

/// <param name="bitmap">Input bitmap</param>

/// <param name="destStream">Stream holding the data</param>

/// <returns>Lengths of the encoded data</returns>

public static int WriteJPEG(Bitmap bitmap, Stream destStream) {

//encode the bitmap in JPEG to the buffer

int startPosition = (int)destStream.Position;

bitmap.Save(destStream, ENCODER_JPEG, ENCODER_JPEG_PARAMS);

int endPosition = (int)destStream.Position;

//return the length

return endPosition - startPosition;

}

/// <summary>

/// Encodes a bitmap to PNG and writes it to a stream.

/// </summary>

/// <param name="bitmap"></param>

/// <param name="destStream"></param>

/// <returns>Lengths of the encoded data</returns>

public static int WritePNG(Bitmap bitmap, Stream destStream) {

//encode the bitmap to PNG

MemoryStream buffer = new MemoryStream();

if (bitmap.PixelFormat != PixelFormat.Format24bppRgb) {

//Converts to a 3 channels RGB bitmmap as ARGB is not unsupported

using (Bitmap tmpBitmap = ImgExt.RemoveAlphaChannel(bitmap)) {

tmpBitmap.Save(buffer, ENCODER_PNG, null);

}

} else {

bitmap.Save(buffer, ENCODER_PNG, null);

}

var bytes = buffer.GetBuffer();

//Since a PDF file doesn't support the PNG format, the encoded chunks need

//to be extracted from it.

//PNG chunk: [length 4 bytes BE][type 4 bytes][data of length][CRC 4bytes]

int imageLength = 0;

int offset = 8; //starts reading just after the 8 bytes signature

int offsetBreak = (int)buffer.Position - 8; //max length - min read length in a loop

while (offset < offsetBreak) {

//read the length on 4 bytes BE

int chunkLength = ReadInt32BE(bytes, offset);

//read the type on 4 bytes

int chunkType = ReadInt32BE(bytes, offset + 4);

if (chunkType == 0x49444154) { //if chunkType equals "IDAT"

//Writes the chunk to the stream

destStream.Write(bytes, offset + 8, chunkLength);

imageLength += chunkLength;

}

//move to the next chunk

offset += chunkLength + 12;

}

return imageLength;

}

private static int ReadInt32BE(byte[] bytes, int offset) {

return bytes[offset] << 24

| bytes[offset + 1] << 16

| bytes[offset + 2] << 8

| bytes[offset + 3];

}

}

}