We Keep Coding

MVC WebAPI return multiple images

I have 3 images in a directory but my code always returns one of them. I'd like to return 3 images image1.jpg, image2.jpg, image3.jpg and get them in my Xamarin app.
I think returning the result like an array might solve the problem but I don't understand what I need.
var result = new HttpResponseMessage(HttpStatusCode.OK);
MemoryStream ms = new MemoryStream();
for (int i = 0; i < 3; i++)
{
String filePath = HostingEnvironment.MapPath("~/Fotos/Empresas/Comer/" + id + (i + 1) + ".jpg");
FileStream fileStream = new FileStream(filePath, FileMode.OpenOrCreate);
Image image = Image.FromStream(fileStream);
image.Save(ms, ImageFormat.Jpeg);
fileStream.Close();
byte[] bytes = File.ReadAllBytes(filePath);
byte[] length = BitConverter.GetBytes(bytes.Length);
// Write length followed by file bytes to stream
ms.Write(length, 0, 3);
ms.Write(bytes, 0, bytes.Length);
}
result.Content = new StreamContent(ms);
return result;
Now i getting bytes, i edit a little bit the code now
byte[] imageAsBytes = client.GetByteArrayAsync(url).Result;
MemoryStream stream1 = new MemoryStream(imageAsBytes);
img.Source = ImageSource.FromStream(() => { return stream1; });
this is my xamarin code to get images, but i still getting nothing =/

If you just return a memorystream is not easy to differentiate one image from the other in the stream, instead of this, you can return a List of byte arrays, then you can access each position in the array and convert from byte array to image...
Here is a fully functional dotnet core webapi controller :
public class GetImagesController : Controller
{
private readonly IWebHostEnvironment _host;
public GetImagesController(IWebHostEnvironment host)
{
_host = host;
}
[HttpGet("{images}")]
public async Task<List<byte[]>> Get([FromQuery]string images)
{
List<byte[]> imageBytes = new List<byte[]>();
String[] strArray = images.Split(',');
for (int i = 0; i < strArray.Length; i++)
{
String filePath = Path.Combine(_host.ContentRootPath, "images", strArray[i]+".jpg");
byte[] bytes = System.IO.File.ReadAllBytes(filePath);
imageBytes.Add(bytes);
}
return imageBytes;
}
}
This controller can be called like this :
https://localhost:44386/getImages?images=P1,P2,P3
Given that you have a folder called images with files P1.jpg, P2.jpg and P3.jpg under your ContentRooPath.
https://learn.microsoft.com/en-us/aspnet/core/fundamentals/host/web-host?view=aspnetcore-3.0

You'll need something in the response to delimit where each image starts and finishes. As a basic solution, you could write the image length as an Int32 and follow it with the image data. On the other end, you'll need to read the 4-byte length followed by that x number of bytes:
[HttpGet]
public HttpResponseMessage Get(string id)
{
var result = new HttpResponseMessage(HttpStatusCode.OK);
String[] strArray = id.Split(',');
var ms = new MemoryStream();
for (int i = 0; i < strArray.Length; i++)
{
String filePath = HostingEnvironment.MapPath("~/Fotos/Empresas/Comer/" + strArray[i] + (i + 1) + ".jpg");
byte[] bytes = File.ReadAllBytes(filePath);
byte[] length = BitConverter.GetBytes(bytes.Length);
// Write length followed by file bytes to stream
ms.Write(length, 0, 4);
ms.Write(bytes, 0, bytes.Length);
}
result.Content = new StreamContent(ms);
return result;
}

FileStream is not working with relative path

I'm trying to use a FileStream with a relative path but it is not working.
var pic = ReadFile("~/Images/money.png");
It is working when I use something like:
var p = GetFilePath();
var pic = ReadFile(p);
the rest of the code(from SO):
public static byte[] ReadFile(string filePath)
{
byte[] buffer;
FileStream fileStream = new FileStream(filePath, FileMode.Open, FileAccess.Read);
try
{
int length = (int)fileStream.Length; // get file length
buffer = new byte[length]; // create buffer
int count; // actual number of bytes read
int sum = 0; // total number of bytes read
// read until Read method returns 0 (end of the stream has been reached)
while ((count = fileStream.Read(buffer, sum, length - sum)) > 0)
sum += count; // sum is a buffer offset for next reading
}
finally
{
fileStream.Close();
}
return buffer;
}
public string GetFilePath()
{
return HttpContext.Current.Server.MapPath("~/Images/money.png");
}
I don't get why it is not working because the FileStream constructor allow using relative path.

I'm assuming the folder in your program has the subfolder images, which contains your image file.
\folder\program.exe
\folder\Images\money.jpg
Try without the "~".

I also had the same issue but I solved it by using this code,
Try one of this code, hope it will solve your issue too.
#region GetImageStream
public static Stream GetImageStream(string Image64string)
{
Stream imageStream = new MemoryStream();
if (!string.IsNullOrEmpty(Image64string))
{
byte[] imageBytes = Convert.FromBase64String(Image64string.Substring(Image64string.IndexOf(',') + 1));
using (Image targetimage = BWS.AWS.S3.ResizeImage(System.Drawing.Image.FromStream(new MemoryStream(imageBytes, false)), new Size(1600, 1600), true))
{
targetimage.Save(imageStream, ImageFormat.Jpeg);
}
}
return imageStream;
}
#endregion
2nd one
#region GetImageStream
public static Stream GetImageStream(Stream stream)
{
Stream imageStream = new MemoryStream();
if (stream != null)
{
using (Image targetimage = BWS.AWS.S3.ResizeImage(System.Drawing.Image.FromStream(stream), new Size(1600, 1600), true))
{
targetimage.Save(imageStream, ImageFormat.Jpeg);
}
}
return imageStream;
}
#endregion

C# - Compress byte[]

I receive a zip file base64 string, convert to byte[], open in memory, modify content, and then 'compress' the new byte[] to base64 string again.
My problem, I don't know how to 'compress' the new byte[] to zip format.
public string ModifyZipContent(string base64) {
ZipPackage zipPackage = null;
MemoryStream memoryStream = null;
long lenght;
byte[] data = Convert.FromBase64String(base64);
byte[] buffer;
byte[] newData;
int arrayOffset = 0;
memoryStream = new MemoryStream();
memoryStream.Write(data, 0, data.Length);
zipPackage = (ZipPackage)Package.Open(memoryStream, FileMode.Open);
PackagePartCollection zipParts = zipPackage.GetParts();
// this is awful
foreach(ZipPackagePart zipPart in zipParts) {
using(Stream stream = zipPart.GetStream()) {
arrayOffset += (int)stream.Length;
}
}
newData = new byte[arrayOffset];
// end
arrayOffset = 0;
foreach(ZipPackagePart zipPart in zipParts) {
using(Stream stream = zipPart.GetStream()) {
lenght = stream.Length;
buffer = new byte[lenght];
stream.Read(buffer, 0, (int)lenght);
Buffer.BlockCopy(buffer, 0, newData, arrayOffset, buffer.Length);
arrayOffset += buffer.Length;
}
}
return Convert.ToBase64String(newData);
}

I haven't fully tested this, but something along these lines should work...
// Requires System.IO.Compression using statement.
byte[] bytes = new byte[256]; // Your byte[] would be here instead of this empty one.
using (var zipFile = ZipFile.Open("C:/ZipFile.zip", ZipArchiveMode.Update))
{
var entry = zipFile.CreateEntry("YourEntryPathHere");
using (var stream = entry.Open())
{
stream.Write(bytes, 0, bytes.Length);
}
}

zlib.net code example for C# that take byte[] as input agument

I spent 3 hours searching for how to uncompress a string using Zlib.net.dll and I did not find anything useful.
Since my string is compressed by the old VB6 program that uses zlib.dll and I do not want to use file access each time I want to uncompress a string.
The problem is you need to know what the original size of the byte[] is before compression.
Or you can use dynamic array for decoding the data.
The code is here:
private string ZlibNetDecompress(string iCompressData, uint OriginalSize)
{
byte[] todecode_byte = Convert.FromBase64String(iCompressData);
byte[] lDecodeData = new byte[OriginalSize];
string lTempoString = System.Text.Encoding.Unicode.GetString(todecode_byte);
todecode_byte = System.Text.Encoding.Default.GetBytes(lTempoString);
string lReVal = "";
MemoryStream outStream = new MemoryStream();
MemoryStream InStream = new MemoryStream(todecode_byte);
zlib.ZOutputStream outZStream = new zlib.ZOutputStream(outStream);
try
{
CopyStream(InStream, outZStream);
lDecodeData = outStream.GetBuffer();
lReVal = System.Text.Encoding.Default.GetString(lDecodeData);
}
finally
{
outZStream.Close();
InStream.Close();
}
return lReVal;
}
private void CopyStream(System.IO.Stream input, System.IO.Stream output)
{
byte[] buffer = new byte[2000];
int len;
while ((len = input.Read(buffer, 0, 2000)) > 0)
{
output.Write(buffer, 0, len);
}
output.Flush();
}

You could use the GZipStreamClass from the framework.
var data = new byte[resultSizeMax];
using (Stream ds = new DeflateStream(stream, CompressionMode.Decompress))
for (var i=0; i< 1000; i+=ds.Read(data, i,1000-i);

Problem with C# Decompression

Have some data in a sybase image type column that I want to use in a C# app. The data has been compressed by Java using the java.util.zip package. I wanted to test that I could decompress the data in C#. So I wrote a test app that pulls it out of the database:
byte[] bytes = (byte[])reader.GetValue(0);
This gives me a compressed byte[] of 2479 length.
Then I pass this to a seemingly standard C# decompression method:
public static byte[] Decompress(byte[] gzBuffer)
{
MemoryStream ms = new MemoryStream();
int msgLength = BitConverter.ToInt32(gzBuffer, 0);
ms.Write(gzBuffer, 4, gzBuffer.Length - 4);
byte[] buffer = new byte[msgLength];
ms.Position = 0;
GZipStream zip = new GZipStream(ms, CompressionMode.Decompress);
zip.Read(buffer, 0, buffer.Length);
return buffer;
}
The value for msgLength is 1503501432 which seems way out of range. The original document should be in the range of 5K -50k. Anyway when I use that value to create "buffer" not surprisingly I get an OutOfMemoryException.
What is happening?
Jim
The Java compress method is as follows:
public byte[] compress(byte[] bytes) throws Exception {
byte[] results = new byte[bytes.length];
Deflater deflator = new Deflater();
deflater.setInput(bytes);
deflater.finish();
int len = deflater.deflate(results);
byte[] out = new byte[len];
for(int i=0; i<len; i++) {
out[i] = results[i];
}
return(out);
}

As I cant see your java code, I can only guess you are compressing your data to a zip file stream. Therefore it will obviously fail if you are trying to decompress that stream with a gzip decompression in c#. Either you change your java code to a gzip compression (Example here at the bottom of the page), or you decompress the zip file stream in c# with an appropriate library (e.g. SharpZipLib).
Update
Ok now, I see you are using deflate for the compression in java. So, obviously you have to use the same algorithm in c#: System.IO.Compression.DeflateStream
public static byte[] Decompress(byte[] buffer)
{
using (MemoryStream ms = new MemoryStream(buffer))
using (Stream zipStream = new DeflateStream(ms,
CompressionMode.Decompress, true))
{
int initialBufferLength = buffer.Length * 2;
byte[] buffer = new byte[initialBufferLength];
bool finishedExactly = false;
int read = 0;
int chunk;
while (!finishedExactly &&
(chunk = zipStream.Read(buffer, read, buffer.Length - read)) > 0)
{
read += chunk;
if (read == buffer.Length)
{
int nextByte = zipStream.ReadByte();
// End of Stream?
if (nextByte == -1)
{
finishedExactly = true;
}
else
{
byte[] newBuffer = new byte[buffer.Length * 2];
Array.Copy(buffer, newBuffer, buffer.Length);
newBuffer[read] = (byte)nextByte;
buffer = newBuffer;
read++;
}
}
}
if (!finishedExactly)
{
byte[] final = new byte[read];
Array.Copy(buffer, final, read);
buffer = final;
}
}
return buffer;
}