How to load a part of a TIFF image without loading whole image into memory?

Question

How to load a part of a *.tif image without loading this image into memory.

I have to work with big TIFF files. (> 4 GB). I tried to read this file using BinaryReader , and using BitMiracle.LibTiff.Classic to convert bytes into image. But I didn't find example for how to read a specific pixel in a TIFF file.

Maybe be you have some solution for this task.

Lets say i have a BigScan.tif file and it is always:

Image Compression -  NONE
Pixel Order       -  Interleaved (RGBRGB)
Byte Order        -  IBM PC

I have some variable:

ImagePart with  User Defined Width
ImagePart with  User Define Height
ImagePArt with  User Defined Location

The question is, how could I get ImagePart from BigScan.tif ?

But it would be best to have the ability to read information of the pixel in "BigScan.tif" with (x,y) coorinates.

I need to read a pixel from the BigScan.tif in specified place, with such function:

public Color GetPixelColorFromTiffImage(string TiffFileName, int PixelPositionX, int PixelPositionY)
{
    //Some Code
   return returnedColor;
}

---

Very strange but the support did`t unswer my quastion. May be somebody knows it. Why dose this part of the code from BitMiracle Samples wrote to 'raster' array numbers like "-11512229", "-11838376" and so on.

 using (Tiff image = Tiff.Open(fullImageLocation, "r"))
        {

            // Find the width and height of the image
            FieldValue[] value = image.GetField(TiffTag.IMAGEWIDTH);
             width = value[0].ToInt();

            value = image.GetField(TiffTag.IMAGELENGTH);
            height = value[0].ToInt();

            int imageSize = height * width;
            int[] raster = new int[imageSize];


            // Read the image into the memory buffer
            if (!image.ReadRGBAImage(width, height, raster))
            {
                MessageBox.Show("Could not read image");

            }


            using (Bitmap btm = new Bitmap(200, 200))
            {
                for (int i = 0; i < btm.Width; ++i)
                    for (int j = 0; j < btm.Height; ++j)
                        btm.SetPixel(i, j, getSample(i + 330, j + 30, raster, width, height));

                ReternedBitmap = btm;
            }
        }//using    

Answer 1

Your question is unclear (you ask at least two different questions).

If you need to crop a part of a larger image then you need to:

1. read each relevant scanline of a source image
2. copy part of that scanline to a new image.

If you need to get color value of a single pixel in a given location than again you need to:

1. read relevant scanline
2. find relevant bytes in that scanline
3. pack those bytes into a Color structure or whatever else

You didn't specify what are Photometric , BitsPerSample and SamplesPerPixel values for your image, so it's hard to tell what exactly are you dealing with.

Most probably, you are faced with geo-images. If so, they are probably RGB, 24bit, tiled images.

For tiled images it is possible to read only small part (say, 256 x 256 pixels) of the image at once. But even if they are stripped, one scanline of such an image will take only about 1 MB of memory (219 000 pixels * 3 bytes per pixel). It's nothing if you are really need to process such big images.

I wouldn't recommend you to try developing your own parser. It's not that easy if you know only basics about TIFF format.