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File.ReadAllBytes doesn't read the PNG image pixels properly

I am trying to read the bytes of a .png image using File.ReadAllBytes(string) method without success.
My images are of size 2464x2056x3 (15.197.952 bytes), but this method returns an array of about 12.000.000 bytes.
I tried with a white image of the same size, and I am getting a byte array of 25.549, and checking the byte array I can see all kind of values, that obviously is not correct because is a white image.
The code I am using is:
var frame = File.ReadAllBytes("C:\\workspace\\white.png");
I've also tried to open the image first as an Image object then get the byte array with the following:
using (var ms = new MemoryStream())
{
var imageIn = Image.FromFile("C:\\workspace\\white.png");
imageIn.Save(ms, imageIn.RawFormat);
var array = ms.ToArray();
}
But the result is the same as before...
Any idea of what's happening?
How can I read the byte array?

PNG is a compressed format.
See some info about it: Portable Network Graphics - Wikipedia.
This means that the binary representation is not the actual pixel values that you expect.
You need some kind of a PNG decoder to get the pixel values from the compressed data.
This post might steer you in the right direction: Reading a PNG image file in .Net 2.0. Note that it's quite old, maybe there are newer methods for doing it.
On a side note: even a non compressed format like BMP has a header, so you can't simply read the binary file and get the pixel values in a trivial way.
Update:
One way to get the pixel values from a PNG file is demonstrated below:
using System.Drawing.Imaging;
byte[] GetPngPixels(string filename)
{
byte[] rgbValues = null;
// Load the png and convert to Bitmap. This will use a .NET PNG decoder:
using (var imageIn = Image.FromFile(filename))
using (var bmp = new Bitmap(imageIn))
{
// Lock the pixel data to gain low level access:
BitmapData bmpData = bmp.LockBits(new Rectangle(0, 0, bmp.Width, bmp.Height), ImageLockMode.ReadWrite, bmp.PixelFormat);
// Get the address of the first line.
IntPtr ptr = bmpData.Scan0;
// Declare an array to hold the bytes of the bitmap.
int bytes = Math.Abs(bmpData.Stride) * bmp.Height;
rgbValues = new byte[bytes];
// Copy the RGB values into the array.
System.Runtime.InteropServices.Marshal.Copy(ptr, rgbValues, 0, bytes);
// Unlock the pixel data:
bmp.UnlockBits(bmpData);
}
// Here rgbValues is an array of the pixel values.
return rgbValues;
}
This method will return a byte array with the size that you expect.
In order to use the data with opencv (or any similar usage), I advise you to enhance my code example and return also the image metadata (width, height, stride, pixel-format). You will need this metadata to construct a cv::Mat.

Resize jpeg stream on memory with .NET, C#

I'm working with WPF, .NET 3.5, C#. I have jpeg file byte array in memory loaded from database, and I'd like to resize it to smaller size on memory.
input is jpeg file byte array in memory.
output is jpeg file byte array in memory, presenting resized jpeg image.
resize (and re-encode) should be done on memory, without using FILE.
resize can be done with bi-liner operation.
Please help me to do this.

A quick google search yields an MSDN article stating how to do this.
A simple example:
System.Drawing.Image source = System.Drawing.Image.FromFile(#"Z:\Temp\temp.bmp");
System.Drawing.Image destination = new System.Drawing.Bitmap(128, 128);
using (var g = Graphics.FromImage(destination))
{
g.InterpolationMode = InterpolationMode.HighQualityBilinear;
g.DrawImage(source, new System.Drawing.Rectangle(0,0,128,128), new System.Drawing.Rectangle(0, 0,source.Width, source.Height), GraphicsUnit.Pixel);
}
destination.Save(#"Z:\Temp\outpt.png", ImageFormat.Png);
Note my example uses files, but that is just for the loading and saving. All of the work is done in memory and you can load and save from memory streams if that suits your workflow better.

You also can use this function :
public static BitmapImage BitmapImageFromBitmapSourceResized(BitmapSource bitmapSource, int newWidth)
{
BmpBitmapEncoder encoder = new BmpBitmapEncoder();
MemoryStream memoryStream = new MemoryStream();
BitmapImage bImg = new BitmapImage();
encoder.Frames.Add(BitmapFrame.Create(bitmapSource));
encoder.Save(memoryStream);
bImg.BeginInit();
bImg.StreamSource = new MemoryStream(memoryStream.ToArray());
bImg.DecodePixelWidth = newWidth;
bImg.EndInit();
memoryStream.Close();
return bImg;
}
The use of this function is recommanded by microsoft, because the image is not saved in its original size but with the size newWidth. It can avoid you memory overflow if the user enter huge images.

Conversion of memory stream to bitmapdata

I make a webrequest to receive a large jpeg as a byte array. This in turn can be converted to a memory stream. I need to get this data into a bitmapdata so that I can marshall copy it to a byte array again. Am i right in assuming that a byte array returned from a memory stream is not the same as a byte array returned from a marshall copy of bitmapdata to a byte array?
I do not want to write the memory stream out to an image as it will return a out of memory error due to its size AND the fact I am using compact cf C# 2.
this is my call to the server..
HttpWebRequest _request = (HttpWebRequest)WebRequest.Create("A url/00249.jpg");
_request.Method = "GET";
_request.Timeout = 5000;
_request.ReadWriteTimeout = 20000;
byte[] _buffer;
int _blockLength = 1024;
int _bytesRead = 0;
MemoryStream _ms = new MemoryStream();
using (Stream _response = ((HttpWebResponse)_request.GetResponse()).GetResponseStream())
{
do
{
_buffer = new byte[_blockLength];
_bytesRead = _response.Read(_buffer, 0, _blockLength);
_ms.Write(_buffer, 0, _bytesRead);
} while (_bytesRead > 0);
}
This is my code to read a byte array from a bitmapdata.
Bitmap Sprite = new Bitmap(_file);
Bitmapdata RawOriginal = Sprite.LockBits(new Rectangle(0, 0, Sprite.Width, Sprite.Height), ImageLockMode.ReadOnly, PixelFormat.Format32bppRgb);
int origByteCount = RawOriginal.Stride * RawOriginal.Height;
SpriteBytes = new Byte[origByteCount];
System.Runtime.InteropServices.Marshal.Copy(RawOriginal.Scan0, SpriteBytes, 0, origByteCount);
Sprite.UnlockBits(RawOriginal);
Note:
I do not want to use this:
Bitmap Sprite = new Bitmap(_file);
I want to go from:
MemoryStream _ms = new MemoryStream();
to
System.Runtime.InteropServices.Marshal.Copy(RawOriginal.Scan0, SpriteBytes, 0, origByteCount);
using what ever conversions are required without writing to a bitmap.

What you're asking is going to be difficult. The data you're receiving from the response object is a full jpeg image, which has a header and then a bunch of compressed data bytes. The byte array addressed by Scan0 is uncompressed and quite possibly includes some padding bytes at the end of each scan line.
Most importantly, you definitely cannot use Marshal.Copy to copy the received bytes to Scan0.
To do what you're asking will require that you parse the header of the jpeg that you receive and uncompress the image bits directly to Scan0, padding each scan line as appropriate. There is nothing in the .NET Framework that will do that for you.
The accepted answer to this question has a link to a library that might help you out.
Even if that works, I'm not certain it will help you out. If calling the BitMap constructor to create the image causes you to run out of memory, it's almost certain that this roundabout method will, as well.
Is the problem that you have so many sprites that you can't keep them all in memory, uncompressed? If so, you'll probably have to find some other way to solve your problem.
By the way, you can save yourself a lot of trouble by changing your code that reads the image to:
MemoryStream _ms = new MemoryStream();
using (Stream _response = ((HttpWebResponse)_request.GetResponse()).GetResponseStream())
{
_response.CopyTo(_ms);
}

Got Reversed Image from Byte Array when converting to Base64

I need to get the raw bitmap data only (no header, or other information). I used the following code to get the bitmap data:
using (Bitmap bitmap = svgDocument.Draw())
{
Rectangle rect = new Rectangle(0, 0, bitmap.Width, bitmap.Height);
BitmapData bitmapData = bitmap.LockBits(rect, ImageLockMode.ReadWrite, bitmap.PixelFormat);
var length = Math.Abs(bitmapData.Stride) * bitmapData.Height;
byte[] bytes = new byte[length];
Marshal.Copy(bitmapData.Scan0, bytes, 0, length);
bitmap.UnlockBits(bitmapData);
MemoryStream memoryStream = new MemoryStream();
string filename = DateTime.Now.Ticks.ToString() + ".bmp"; // this works fine
bitmap.Save(filename, ImageFormat.Bmp);
string base64 = Convert.ToBase64String(bytes, Base64FormattingOptions.InsertLineBreaks); // the base64 is reversed.
}
When I save the bitmap, everything looks fine. The image is not reversed. However when I use the bytes only to convert the data to Base64, then the image is reversed.
Edit 1:
I think this has nothing to do with the Base64 conversion. It seems that the bytes are in reversed order.
When I save the image using the code, the image looks like this:
When I use the bytes, then I see this:
Solution:
I found the solution. Instead of creating a new bitmap, I just skipped the first 54 bytes of header information and then stored the byte array.
MemoryStream memoryStream = new MemoryStream();
bitmap.Save(memoryStream, ImageFormat.Bmp);
// Skip header
IEnumerable<byte> bytes = memoryStream.ToArray().Skip(54);

The standard BMP format allows to store bytes of the image either in classical top/down order or in reverse order.
The way to tell whether your image is stored this way is to check the value of the Height parameter in the BMP header:
If Height < 0, then the height of your image is abs(Height) and the pixels are stored in reverse (bottom / top) order.
If Height > 0, then you are in the case you expect, where pixels are in 'normal' order, top to bottom.
I would say that what happens in your case is that you are starting from an image stored with a negative Height header (the SVG object must do that for some reason). But you do not check it, so you store the pixels in bottom to top order.
When you store with the BMP object, it figures that out for you from the context. But when you export just the pixels, then the third party application that loads your image sees positive Height and thus shows your image upside down.
You can find details about this pixel ordering in the Wikipedia page for BMP file format.
Edit:
So, when you write a BMP file to your disk, you have to do the following:
Check whether your bytes are in top to bottom order (a) or in bottom to top order (b)
If (a): put the height of your image as a positive value in the BMP header
If (b): put - height as a negative value in the BMP header. So that the third party program that shows your image knows that it's reversed.

I found the solution. Instead of creating a new bitmap, I just skipped the first 54 bytes of header information and then stored the byte array.
MemoryStream memoryStream = new MemoryStream();
bitmap.Save(memoryStream, ImageFormat.Bmp);
// Skip header
IEnumerable<byte> bytes = memoryStream.ToArray().Skip(54);

I ran into the same problem but still needed a base 64 string (for HTML5 canvas). So I used the Image class to rotate the image, stored in a new stream, then convert to base64 string.
var image = System.Drawing.Image.FromStream(new MemoryStream(bytes));
//Rotate and save to new stream
image.RotateFlip(System.Drawing.RotateFlipType.Rotate180FlipNone);
MemoryStream streamOut = new MemoryStream();
image.Save(streamOut, System.Drawing.Imaging.ImageFormat.Jpeg);
//Convert to base64 string
string base64String = Convert.ToBase64String(streamOut.ToArray());

Exctract FlateDecode images using iTextSharp

I want to extract images from an PDF. I'm using iTextSharp right now.
Some images can be extracted correct, but most of them don't have the right colors and are distorted.
I did some experiments with different PixelFormats, but I didn't get a solution for my Problem...
This is the Code which separates the image-types:
if (filter == "/FlateDecode")
{
// ...
int w = int.Parse(width);
int h = int.Parse(height);
int bpp = tg.GetAsNumber(PdfName.BITSPERCOMPONENT).IntValue;
byte[] rawBytes = PdfReader.GetStreamBytesRaw((PRStream)tg);
byte[] decodedBytes = PdfReader.FlateDecode(rawBytes);
byte[] streamBytes = PdfReader.DecodePredictor(decodedBytes, tg.GetAsDict(PdfName.DECODEPARMS));
PixelFormat[] pixFormats = new PixelFormat[23] {
PixelFormat.Format24bppRgb,
// ... all Pixel Formats
};
for (int i = 0; i < pixFormats.Length; i++)
{
Program.ToPixelFormat(w, h, pixFormats[i], streamBytes, bpp, images));
}
}
This is the Code to save the Image in a MemoryStream. Saving the image in a folder is implemented later.
private static void ToPixelFormat(int width, int height, PixelFormat pixelformat, byte[] bytes, int bpp, IList<Image> images)
{
Bitmap bmp = new Bitmap(width, height, pixelformat);
BitmapData bmd = bmp.LockBits(new Rectangle(0, 0, width, height),
ImageLockMode.WriteOnly, pixelformat);
Marshal.Copy(bytes, 0, bmd.Scan0, bytes.Length);
bmp.UnlockBits(bmd);
using (var ms = new MemoryStream())
{
bmp.Save(ms, System.Drawing.Imaging.ImageFormat.Tiff);
bytes = ms.GetBuffer();
}
images.Add(bmp);
}
Please help me.

even you found solution for your problem, let me say suggestion to fix your code above.
I believe the distortion problem is caused because of mismatch in row data boundary. PdfReader returns data in a byte boundary. For example for grayscale image 20 pixel wide you will get 20 bytes of data for each image row. Bitmap class works with 32bit boundary. When creating bitmap with 20 pixels of width, Bitmap class will generate grayscale bitmap with stride(byte width)=32 bytes. It means you cannot simply copy the retrieved bytes from PdfReader into a new bitmap using Marshal.Copy() method as it is in your ToPixelFormat().
First pixel in source byte array is located as 21st byte but destination Bitmap needs it as 33rd byte becasue of the 32bit boundary of the Bitmap. To solve this issue I had to create byte array with size that considers the 32bit boundary for each data row.
Copy data row by row from bytes aray retrieved from PdfReader into new byte array with 32bit row boundary consideration. Now I had bytes of data with boundary that matched the Bitmap class boundary so I can copy it to the new Bitmap using Marshal.Copy().

I found an solution for my own problem.
To extract all Images on all Pages, it is not necessary to implement different filters.
iTextSharp has an Image Renderer, which saves all Images in their original image type.
Just do the following found here: http://kuujinbo.info/iTextSharp/CCITTFaxDecodeExtract.aspx
You don't need to implement HttpHandler...

PDF supports a pretty wide variety of image formats. I don't think I would take this approach you've chosen here. You need to determine the image format from the bytes in the stream itself. For example, JPEG will typically start with the ASCII bytes JFIF.
.NET (3.0+) does come with a method that will attempt to pick the right decoder: BitmapDecoder.Create. See http://msdn.microsoft.com/en-us/library/system.windows.media.imaging.bitmapdecoder.aspx
If that doesn't work you may want to consider some third-party imaging libraries. I've used ImageMagick.NET and LeadTools (way overpriced).