Сохранить изображение как .bmp Файл [дубликат]

Обратите внимание, что код выше очень медленный. Я обнаружил, что для оптимизации вышеописанного кода необходимо сделать массив байтов для хранения всех данных до его размещения. Конечно, я работал в Xamarin C #, поэтому, возможно, именно поэтому. Во всяком случае, вот мой код Xamarin, если у кого-то такая же проблема.

      public class AndroidBmpUtil
        {

            private static int BMP_WIDTH_OF_TIMES = 4;
            private static int BYTE_PER_PIXEL = 3;

            /**
             * Android Bitmap Object to Window's v3 24bit Bmp Format File
             * @param orgBitmap
             * @param filePath
             * @return file saved result
             */
            public static byte[] ConvertAndroidBitmapByteArray(Bitmap orgBitmap, String filePath)
            {
                if (orgBitmap == null)
                {
                    return null;
                }

                if (filePath == null)
                {
                    return null;
                }

                //image size
                int width = orgBitmap.Width;
                int height = orgBitmap.Height;

                //image dummy data size
                //reason : the amount of bytes per image row must be a multiple of 4 (requirements of bmp format)
                byte[] dummyBytesPerRow = null;
                bool hasDummy = false;
                int rowWidthInBytes = BYTE_PER_PIXEL * width; //source image width * number of bytes to encode one pixel.
                if (rowWidthInBytes % BMP_WIDTH_OF_TIMES > 0)
                {
                    hasDummy = true;
                    //the number of dummy bytes we need to add on each row
                    dummyBytesPerRow = new byte[(BMP_WIDTH_OF_TIMES - (rowWidthInBytes % BMP_WIDTH_OF_TIMES))];
                    //just fill an array with the dummy bytes we need to append at the end of each row
                    for (int i = 0; i < dummyBytesPerRow.Length; i++)
                    {
                        dummyBytesPerRow[i] = (byte)0xFF;
                    }
                }

                //an array to receive the pixels from the source image
                int[] pixels = new int[width * height];

                //the number of bytes used in the file to store raw image data (excluding file headers)
                int imageSize = (rowWidthInBytes + (hasDummy ? dummyBytesPerRow.Length : 0)) * height;
                //file headers size
                int imageDataOffset = 0x36;

                //final size of the file
                int fileSize = imageSize + imageDataOffset;

                //Android Bitmap Image Data
                orgBitmap.GetPixels(pixels, 0, width, 0, 0, width, height);

                //ByteArrayOutputStream baos = new ByteArrayOutputStream(fileSize);
                ByteBuffer buffer = ByteBuffer.Allocate(fileSize);

                /**
                 * BITMAP FILE HEADER Write Start
                 **/
                buffer.Put((sbyte)0x42);
                buffer.Put((sbyte)0x4D);

                //size
                buffer.Put(writeInt(fileSize));

                //reserved
                buffer.Put(writeShort((short)0));
                buffer.Put(writeShort((short)0));

                //image data start offset
                buffer.Put(writeInt(imageDataOffset));

                /** BITMAP FILE HEADER Write End */

                //*******************************************

                /** BITMAP INFO HEADER Write Start */
                //size
                buffer.Put(writeInt(0x28));

                //width, height
                //if we add 3 dummy bytes per row : it means we add a pixel (and the image width is modified.
                buffer.Put(writeInt(width + (hasDummy ? (dummyBytesPerRow.Length == 3 ? 1 : 0) : 0)));
                buffer.Put(writeInt(height));

                //planes
                buffer.Put(writeShort((short)1));

                //bit count
                buffer.Put(writeShort((short)24));

                //bit compression
                buffer.Put(writeInt(0));

                //image data size
                buffer.Put(writeInt(imageSize));

                //horizontal resolution in pixels per meter
                buffer.Put(writeInt(0));

                //vertical resolution in pixels per meter (unreliable)
                buffer.Put(writeInt(0));

                buffer.Put(writeInt(0));

                buffer.Put(writeInt(0));

                /** BITMAP INFO HEADER Write End */
                int row = height;
                int col = width;
                int startPosition = (row - 1) * col;
                int endPosition = row * col;

                // This while loop is a lengthy process
                // Puts take a while so only do one by creating a big array called final
                byte[] final = new byte[0];
                while (row > 0)
                {
                    // This array is also used to cut down on time of puts
                    byte[] b = new byte[(endPosition - startPosition)*3];
                    int counter = 0;
                    for (int i = startPosition; i < endPosition; i++)
                    {

                        b[counter] = (byte)((pixels[i] & 0x000000FF));
                        b[counter + 1] = (byte)((pixels[i] & 0x0000FF00) >> 8);
                        b[counter + 2] = (byte)((pixels[i] & 0x00FF0000) >> 16);
                        counter += 3;
                    }
                    int finalPriorLength = final.Length;
                    Array.Resize<byte>(ref final, finalPriorLength + b.Length);
                    Array.Copy(b, 0, final, finalPriorLength, b.Length);

                    if (hasDummy)
                    {
                        finalPriorLength = final.Length;
                        Array.Resize<byte>(ref final, finalPriorLength + dummyBytesPerRow.Length);
                        Array.Copy(dummyBytesPerRow, 0, final, finalPriorLength, dummyBytesPerRow.Length);
                    }
                    row--;
                    endPosition = startPosition;
                    startPosition = startPosition - col;
                }
                buffer.Put(final);
                buffer.Rewind();

                IntPtr classHandle = JNIEnv.FindClass("java/nio/ByteBuffer");
                IntPtr methodId = JNIEnv.GetMethodID(classHandle, "array", "()[B");
                IntPtr resultHandle = JNIEnv.CallObjectMethod(buffer.Handle, methodId);
                byte[] result = JNIEnv.GetArray<byte>(resultHandle);
                JNIEnv.DeleteLocalRef(resultHandle);

                return result;
            }

            /**
             * Write integer to little-endian
             * @param value
             * @return
             * @throws IOException
             */
            private static byte[] writeInt(int value)
            {
                byte[] b = new byte[4];

                b[0] = (byte)(value & 0x000000FF);
                b[1] = (byte)((value & 0x0000FF00) >> 8);
                b[2] = (byte)((value & 0x00FF0000) >> 16);
                b[3] = (byte)((value & 0xFF000000) >> 24);

                return b;
            }

            /**
             * Write short to little-endian byte array
             * @param value
             * @return
             * @throws IOException
             */
            private static byte[] writeShort(short value)
            {
                byte[] b = new byte[2];

                b[0] = (byte)(value & 0x00FF);
                b[1] = (byte)((value & 0xFF00) >> 8);

                return b;
            }
        }
    }

Чтобы использовать его, это код вызова:

using (FileStream outStream = new    FileStream(@yourFilePath, FileMode.Create))
{
    Bitmap Signature = Bitmap.CreateBitmap(user defined values...); 
    byte[] buffer = AndroidBmpUtil.ConvertAndroidBitmapByteArray(Signature, @yourFilePath); 

    // Actually create the file                                 
    outStream.Write(buffer, 0, buffer.Length);
}

Код для конвертирования объекта Bitmap для Android в файл 8 бит bmp. Он получен из этого проекта C #: https://www.codeproject.com/articles/70442/c-rgb-to-palette-based-bit-greyscale-bitmap-clas

import android.graphics.Bitmap;
import android.graphics.Color;


public class BitmapConvertor {

    private  byte[] Color_palette = new byte[1024]; //a palette containing 256 colors
   private   byte[] BMP_File_Header = new byte[14];
   private  byte[] DIB_header = new byte[40];
  private   byte[] Bitmap_Data = null;


    //returns a byte array of a grey scale bitmap image
    public    byte[] CreateGrayBitmapArray(Bitmap Image) {
        try {
            create_parts(Image);
            //Create the array
            byte[] bitmap_array = new byte[BMP_File_Header.length + DIB_header.length
                    + Color_palette.length + Bitmap_Data.length];
            Copy_to_Index(bitmap_array, BMP_File_Header, 0);
            Copy_to_Index(bitmap_array, DIB_header, BMP_File_Header.length);
            Copy_to_Index(bitmap_array, Color_palette, BMP_File_Header.length + DIB_header.length);
            Copy_to_Index(bitmap_array, Bitmap_Data, BMP_File_Header.length + DIB_header.length + Color_palette.length);

            return bitmap_array;
        } catch (Exception e) {
            return null; //return a null single byte array if fails
        }
    }


    //creates byte array of 256 color grayscale palette
    private   byte[] create_palette() {
        byte[] color_palette = new byte[1024];
        for (int i = 0; i < 256; i++) {
            color_palette[i * 4 + 0] = (byte) (i); //bule
            color_palette[i * 4 + 1] = (byte) (i); //green
            color_palette[i * 4 + 2] = (byte) (i); //red
            color_palette[i * 4 + 3] = (byte) 0; //padding
        }
        return color_palette;
    }


    //adds dtata of Source array to Destinition array at the Index
   private   boolean Copy_to_Index(byte[] destination, byte[] source, int index) {
        try {
            for (int i = 0; i < source.length; i++) {
                destination[i + index] = source[i];
            }
            return true;
        } catch (Exception e) {
            return false;
        }
    }


    //create different part of a bitmap file
  private    void create_parts(Bitmap img) {
        //Create Bitmap Data
        Bitmap_Data = ConvertToGrayscale(img);
        //Create Bitmap File Header (populate BMP_File_Header array)
        Copy_to_Index(BMP_File_Header, new byte[]{(byte) 'B', (byte) 'M'}, 0); //magic number
        Copy_to_Index(BMP_File_Header, writeInt(BMP_File_Header.length
                + DIB_header.length + Color_palette.length + Bitmap_Data.length), 2); //file size
        Copy_to_Index(BMP_File_Header, new byte[]{(byte) 'M', (byte) 'C', (byte) 'A', (byte) 'T'}, 6); //reserved for application generating the bitmap file (not imprtant)
        Copy_to_Index(BMP_File_Header, writeInt(BMP_File_Header.length
                + DIB_header.length + Color_palette.length), 10); //bitmap raw data offset
        //Create DIB Header (populate DIB_header array)
        Copy_to_Index(DIB_header, writeInt(DIB_header.length), 0); //DIB header length
        Copy_to_Index(DIB_header, writeInt(((Bitmap) img).getWidth()), 4); //image width
        Copy_to_Index(DIB_header, writeInt(((Bitmap) img).getHeight()), 8); //image height
        Copy_to_Index(DIB_header, new byte[]{(byte) 1, (byte) 0}, 12); //color planes. N.B. Must be set to 1
        Copy_to_Index(DIB_header, new byte[]{(byte) 8, (byte) 0}, 14); //bits per pixel
        Copy_to_Index(DIB_header, writeInt(0), 16); //compression method N.B. BI_RGB = 0
        Copy_to_Index(DIB_header, writeInt(Bitmap_Data.length), 20); //lenght of raw bitmap data
        Copy_to_Index(DIB_header, writeInt(1000), 24); //horizontal reselution N.B. not important
        Copy_to_Index(DIB_header, writeInt(1000), 28); //vertical reselution N.B. not important
        Copy_to_Index(DIB_header, writeInt(256), 32); //number of colors in the palette
        Copy_to_Index(DIB_header, writeInt(0), 36); //number of important colors used N.B. 0 = all colors are imprtant
        //Create Color palett
        Color_palette = create_palette();
    }


    //convert the color pixels of Source image into a grayscale bitmap (raw data)
  private    byte[] ConvertToGrayscale(Bitmap Source) {
        Bitmap source = (Bitmap) Source;
        int padding = (source.getWidth() % 4) != 0 ? 4 - (source.getWidth() % 4) : 0; //determine padding needed for bitmap file
        byte[] bytes = new byte[source.getWidth() * source.getHeight() + padding * source.getHeight()]; //create array to contain bitmap data with paddin
        for (int y = 0; y < source.getHeight(); y++) {
            for (int x = 0; x < source.getWidth(); x++) {
                int pixel = source.getPixel(x, y);
                int g = (int) (0.3 * Color.red(pixel) + 0.59 * Color.green(pixel) + 0.11 * Color.blue(pixel)); //grayscale shade corresponding to rgb
                bytes[(source.getHeight() - 1 - y) * source.getWidth() + (source.getHeight() - 1 - y) * padding + x] = (byte) g;
            }
            //add the padding
            for (int i = 0; i < padding; i++) {
                bytes[(source.getHeight() - y) * source.getWidth() + (source.getHeight() - 1 - y) * padding + i] = (byte) 0;
            }
        }
        return bytes;
    }


    /**
     * Write integer to little-endian
     *
     * @param value
     * @return
     * @throws IOException
     */
    private  byte[] writeInt(int value) {
        byte[] b = new byte[4];

        b[0] = (byte) (value & 0x000000FF);
        b[1] = (byte) ((value & 0x0000FF00) >> 8);
        b[2] = (byte) ((value & 0x00FF0000) >> 16);
        b[3] = (byte) ((value & 0xFF000000) >> 24);

        return b;
    }
}