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I searched all question about byte array but i always failed. I have never coded c# i am new in this side. Could you help me how to make image file from byte array.
Here is my function which stores byte in array named imageData
public void imageReady( byte[] imageData, int fWidth, int fHeight))
You'll need to get those bytes into a MemoryStream:
Bitmap bmp;
using (var ms = new MemoryStream(imageData))
{
bmp = new Bitmap(ms);
}
That uses the Bitmap(Stream stream) constructor overload.
UPDATE: keep in mind that according to the documentation, and the source code I've been reading through, an ArgumentException will be thrown on these conditions:
stream does not contain image data or is null.
-or-
stream contains a PNG image file with a single dimension greater than 65,535 pixels.
Guys thank you for your help. I think all of this answers works. However i think my byte array contains raw bytes. That's why all of those solutions didnt work for my code.
However i found a solution. Maybe this solution helps other coders who have problem like mine.
static byte[] PadLines(byte[] bytes, int rows, int columns) {
int currentStride = columns; // 3
int newStride = columns; // 4
byte[] newBytes = new byte[newStride * rows];
for (int i = 0; i < rows; i++)
Buffer.BlockCopy(bytes, currentStride * i, newBytes, newStride * i, currentStride);
return newBytes;
}
int columns = imageWidth;
int rows = imageHeight;
int stride = columns;
byte[] newbytes = PadLines(imageData, rows, columns);
Bitmap im = new Bitmap(columns, rows, stride,
PixelFormat.Format8bppIndexed,
Marshal.UnsafeAddrOfPinnedArrayElement(newbytes, 0));
im.Save("C:\\Users\\musa\\Documents\\Hobby\\image21.bmp");
This solutions works for 8bit 256 bpp (Format8bppIndexed). If your image has another format you should change PixelFormat .
And there is a problem with colors right now. As soon as i solved this one i will edit my answer for other users.
*PS = I am not sure about stride value but for 8bit it should be equal to columns.
And also this function Works for me.. This function copies 8 bit greyscale image into a 32bit layout.
public void SaveBitmap(string fileName, int width, int height, byte[] imageData)
{
byte[] data = new byte[width * height * 4];
int o = 0;
for (int i = 0; i < width * height; i++)
{
byte value = imageData[i];
data[o++] = value;
data[o++] = value;
data[o++] = value;
data[o++] = 0;
}
unsafe
{
fixed (byte* ptr = data)
{
using (Bitmap image = new Bitmap(width, height, width * 4,
PixelFormat.Format32bppRgb, new IntPtr(ptr)))
{
image.Save(Path.ChangeExtension(fileName, ".jpg"));
}
}
}
}
Can be as easy as:
var ms = new MemoryStream(imageData);
System.Drawing.Image image = Image.FromStream(ms);
image.Save("c:\\image.jpg");
Testing it out:
byte[] imageData;
// Create the byte array.
var originalImage = Image.FromFile(#"C:\original.jpg");
using (var ms = new MemoryStream())
{
originalImage.Save(ms, ImageFormat.Jpeg);
imageData = ms.ToArray();
}
// Convert back to image.
using (var ms = new MemoryStream(imageData))
{
Image image = Image.FromStream(ms);
image.Save(#"C:\newImage.jpg");
}
In addition, you can simply convert byte array to Bitmap.
var bmp = new Bitmap(new MemoryStream(imgByte));
You can also get Bitmap from file Path directly.
Bitmap bmp = new Bitmap(Image.FromFile(filePath));
This was helpful to me: https://www.tek-tips.com/viewthread.cfm?qid=1264492 (Reference answer)
I understand the question as follows:
I have a byte array that contains pixel data e.g. in RGB format (24bit/pixel)
From this raw pixel data I want to create a Bitmap
This code worked for me:
int width = ...;
int height = ...;
byte[] pixelArray = new byte[] {
// Creation of the actual data is not in the scope of this answer
};
Bitmap bmp = new Bitmap(width, height, System.Drawing.Imaging.PixelFormat.Format32bppRgb);
// Create a BitmapData and lock all pixels to be written
BitmapData bmpData = bmp.LockBits(
new Rectangle(0, 0, bmp.Width, bmp.Height),
ImageLockMode.WriteOnly, bmp.PixelFormat);
// Copy the data from the byte array into BitmapData.Scan0
Marshal.Copy(pixelArray, 0, bmpData.Scan0, pixelArray.Length);
// Unlock the pixels
bmp.UnlockBits(bmpData);
// Do something with your image, e.g. save it to disc
bmp.Save("c:\\temp\\mybmp.bmp", ImageFormat.Bmp);
Based on the accepted answer the OP wanted to interpret imageData byte array as the pixel buffer, rather than an already encoded bitmap stream as the most upvoted answer suggests. And though it works, it contains a lot of copies, as well as palette issues ("And there is a problem with colors right now").
I actually happen to have a drawing library exactly for this purpose (among others). The platform-independent core library allows you to interpret any array of primitive types as a bitmap data:
// Unlike in the accepted answer, no extra buffer allocation or
// array copy happens in the background. Note that we can specify
// a palette for the indexed format so the colors will be interpreted correctly
using var myBitmap = BitmapDataFactory.CreateBitmapData(imageData, new Size(fWidth, fHeight),
stride: fWidth, // stride is same as width because of the 8bpp pixel format
pixelFormat: KnownPixelFormat.Format8bppIndexed,
palette: Palette.Grayscale256());
myBitmap is now an IReadWriteBitmapData instance, allowing a lot of operations (just see the available extension methods). It also offers a pretty fast SetPixel method, which respects the palette so in this particular case it turns any color to grayscale. But if you know the actual pixel format you can also can use the WriteRaw<T> method to access the pixels directly.
And if you use the technology-specific packages such as the one for GDI+ or WPF, then you can simply convert your buffer into known bitmap types such as System.Drawing.Bitmap or System.Windows.Media.WriteableBitmap:
// the accepted answer creates two bitmaps due to the color problems where
// the 2nd one is a 32 bpp image. This solution is much faster, simpler, it avoids
// unnecessary allocations and uses parallel processing internally if possible
var systemBitmap = myBitmap.ToBitmap(); // or ToBitmapAsync, ToWriteableBitmap, etc.
I am receiving the following exception:
Exception thrown:
'System.AccessViolationException' in System.Drawing.dll
When calling the Save function of a Bitmap. The procedure works fine the first time around, but subsequent calls throw this exception.
My application takes a single long image and vertically tiles it out into several separate images. I do this by first breaking out the whole image into bytes, then in a Parallel.For loop I generate the bitmap from a subset byte array.
// Generate Bitmap from width, height and bytes
private Bitmap GenerateBitmap(int width, int height, byte[] bytes)
{
Bitmap bmp = new Bitmap(width, height, Stride(width),
PixelFormat.Format8bppIndexed,
Marshal.UnsafeAddrOfPinnedArrayElement(bytes, 0));
bmp.SetPalette();
return bmp;
}
That is the bitmap generation routine.
Here is the loop body that calls it.
Parallel.For(0, tileCount, i =>
{
byte[] bytes = new byte[imageWidth * tileHeight];
for (int j = 0; j < bytes.Length; j++)
{
bytes[j] = imageBytes[j + (imageWidth * (tileHeight * i))];
}
arr[i] = GenerateBitmap(imageWidth, tileHeight, bytes);
});
And here is the code elsewhere that the exception is thrown.
foreach(Bitmap tile in pattern.Tiles)
{
Console.WriteLine("Creating Tile " + count);
using (Bitmap bmp = new Bitmap(tile))
{
bmp.Save(Globals.patternOutputPath + "tile_" + count + ".png");
}
count += 1;
}
Where Tiles is a property of the pattern that calls the for loop function (which returns a list of Bitmaps).
I am assuming I'm missing some clean up somewhere in here.
Additional info: all images (input and output) are 256 (index) color format.
Edit: The comments below address the problem at hand, and I THINK I've solved the problem. I changed the GenerateBitmap routine to the following and am no longer getting this exception, but I have some more testing to do.
private Bitmap GenerateBitmap(int width, int height, byte[] bytes)
{
Bitmap bmp = new Bitmap(width, height, PixelFormat.Format8bppIndexed);
BitmapData bmpData = bmp.LockBits(new Rectangle(0, 0, bmp.Width, bmp.Height), ImageLockMode.WriteOnly, bmp.PixelFormat);
Marshal.Copy(bytes, 0, bmpData.Scan0, bytes.Length);
bmp.UnlockBits(bmpData);
return bmp;
/*Bitmap bmp = new Bitmap(width, height, Stride(width),
PixelFormat.Format8bppIndexed,
Marshal.UnsafeAddrOfPinnedArrayElement(bytes, 0));
bmp.SetPalette();
return bmp;*/
}
I'm trying to crop a jpeg file using the (x,y) coordinates,width and height and save the output in the same location(i.e replace). I tried the below code but its not working.
public void CropImage(int x, int y, int width, int height)
{
string image_path = #"C:\Users\Admin\Desktop\test.jpg";
var img = Image.FromFile(image_path);
Rectangle crop = new Rectangle(x, y, width, height);
Bitmap bmp = new Bitmap(crop.Width, crop.Height);
using (var gr = Graphics.FromImage(bmp))
{
gr.DrawImage(img, new Rectangle(0, 0, bmp.Width, bmp.Height), crop, GraphicsUnit.Pixel);
}
if (System.IO.File.Exists(image_path))
{
System.IO.File.Delete(image_path);
}
bmp.Save(image_path, ImageFormat.Jpeg);
}
This gives an error like:
An exception of type 'System.IO.IOException' occurred in mscorlib.dll but was not handled in user code
Additional information: The process cannot access the file
'C:\Users\Admin\Desktop\test.jpg' because it is being used by another
process.
When I add img.Dispose() I don't get the above error and I'm able to save it.But it saves the blank image with the given width and height.
Can anyone help me out with this??
public void CropImage(int x, int y, int width, int height)
{
string imagePath = #"C:\Users\Admin\Desktop\test.jpg";
Bitmap croppedImage;
// Here we capture the resource - image file.
using (var originalImage = new Bitmap(imagePath))
{
Rectangle crop = new Rectangle(x, y, width, height);
// Here we capture another resource.
croppedImage = originalImage.Clone(crop, originalImage.PixelFormat);
} // Here we release the original resource - bitmap in memory and file on disk.
// At this point the file on disk already free - you can record to the same path.
croppedImage.Save(imagePath, ImageFormat.Jpeg);
// It is desirable release this resource too.
croppedImage.Dispose();
}
I want to convert a byte array to an image.
This is my database code from where I get the byte array:
public void Get_Finger_print()
{
try
{
using (SqlConnection thisConnection = new SqlConnection(#"Data Source=" + System.Environment.MachineName + "\\SQLEXPRESS;Initial Catalog=Image_Scanning;Integrated Security=SSPI "))
{
thisConnection.Open();
string query = "select pic from Image_tbl";// where Name='" + name + "'";
SqlCommand cmd = new SqlCommand(query, thisConnection);
byte[] image =(byte[]) cmd.ExecuteScalar();
Image newImage = byteArrayToImage(image);
Picture.Image = newImage;
//return image;
}
}
catch (Exception) { }
//return null;
}
My conversion code:
public Image byteArrayToImage(byte[] byteArrayIn)
{
try
{
MemoryStream ms = new MemoryStream(byteArrayIn,0,byteArrayIn.Length);
ms.Write(byteArrayIn, 0, byteArrayIn.Length);
returnImage = Image.FromStream(ms,true);//Exception occurs here
}
catch { }
return returnImage;
}
When I reach the line with a comment, the following exception occurs: Parameter is not valid.
How can I fix whatever is causing this exception?
You are writing to your memory stream twice, also you are not disposing the stream after use.
You are also asking the image decoder to apply embedded color correction.
Try this instead:
using (var ms = new MemoryStream(byteArrayIn))
{
return Image.FromStream(ms);
}
Maybe I'm missing something, but for me this one-liner works fine with a byte array that contains an image of a JPEG file.
Image x = (Bitmap)((new ImageConverter()).ConvertFrom(jpegByteArray));
EDIT:
See here for an updated version of this answer: How to convert image in byte array
public Image byteArrayToImage(byte[] bytesArr)
{
using (MemoryStream memstr = new MemoryStream(bytesArr))
{
Image img = Image.FromStream(memstr);
return img;
}
}
I'd like to note there is a bug in solution provided by #isaias-b.
That solution assume that stride is equal to row length. But it is not always true. Due to memory alignments performed by GDI, stride can be greater then row length. This must be taken into account. Otherwise invalid shifted image will be generated. Padding bytes in each row will be ignored.
The stride is the width of a single row of pixels (a scan line), rounded up to a four-byte boundary.
Fixed code:
using System.Drawing;
using System.Drawing.Imaging;
using System.Runtime.InteropServices;
public static class ImageExtensions
{
public static Image ImageFromRawBgraArray(this byte[] arr, int width, int height, PixelFormat pixelFormat)
{
var output = new Bitmap(width, height, pixelFormat);
var rect = new Rectangle(0, 0, width, height);
var bmpData = output.LockBits(rect, ImageLockMode.ReadWrite, output.PixelFormat);
// Row-by-row copy
var arrRowLength = width * Image.GetPixelFormatSize(output.PixelFormat) / 8;
var ptr = bmpData.Scan0;
for (var i = 0; i < height; i++)
{
Marshal.Copy(arr, i * arrRowLength, ptr, arrRowLength);
ptr += bmpData.Stride;
}
output.UnlockBits(bmpData);
return output;
}
}
To illustrate what it can lead to, let's generate PixelFormat.Format24bppRgb gradient image 101x101:
var width = 101;
var height = 101;
var gradient = new byte[width * height * 3 /* bytes per pixel */];
for (int i = 0, pixel = 0; i < gradient.Length; i++, pixel = i / 3)
{
var x = pixel % height;
var y = (pixel - x) / width;
gradient[i] = (byte)((x / (double)(width - 1) + y / (double)(height - 1)) / 2d * 255);
}
If we will copy entire array as-is to address pointed by bmpData.Scan0, we will get following image. Image shifting because part of image was written to padding bytes, that was ignored. Also that is why last row is incomplete:
But if we will copy row-by-row shifting destination pointer by bmpData.Stride value, valid imaged will be generated:
Stride also can be negative:
If the stride is positive, the bitmap is top-down. If the stride is negative, the bitmap is bottom-up.
But I didn't worked with such images and this is beyond my note.
Related answer: C# - RGB Buffer from Bitmap different from C++
All presented answers assume that the byte array contains data in a known file format representation, like: gif, png or jpg. But i recently had a problem trying to convert byte[]s, containing linearized BGRA information, efficiently into Image objects. The following code solves it using a Bitmap object.
using System.Drawing;
using System.Drawing.Imaging;
using System.Runtime.InteropServices;
public static class Extensions
{
public static Image ImageFromRawBgraArray(
this byte[] arr, int width, int height)
{
var output = new Bitmap(width, height);
var rect = new Rectangle(0, 0, width, height);
var bmpData = output.LockBits(rect,
ImageLockMode.ReadWrite, output.PixelFormat);
var ptr = bmpData.Scan0;
Marshal.Copy(arr, 0, ptr, arr.Length);
output.UnlockBits(bmpData);
return output;
}
}
This is a slightly variation of a solution which was posted on this site.
In one line:
Image.FromStream(new MemoryStream(byteArrayIn));
try (UPDATE)
MemoryStream ms = new MemoryStream(byteArrayIn,0,byteArrayIn.Length);
ms.Position = 0; // this is important
returnImage = Image.FromStream(ms,true);
there is a simple approach as below, you can use FromStream method of an image to do the trick,
Just remember to use System.Drawing;
// using image object not file
public byte[] imageToByteArray(Image imageIn)
{
MemoryStream ms = new MemoryStream();
imageIn.Save(ms,System.Drawing.Imaging.ImageFormat.Gif);
return ms.ToArray();
}
public Image byteArrayToImage(byte[] byteArrayIn)
{
MemoryStream ms = new MemoryStream(byteArrayIn);
Image returnImage = Image.FromStream(ms);
return returnImage;
}
One liner:
Image bmp = (Bitmap)((new ImageConverter()).ConvertFrom(imageBytes));
You haven't declared returnImage as any kind of variable :)
This should help:
public Image byteArrayToImage(byte[] byteArrayIn)
{
try
{
MemoryStream ms = new MemoryStream(byteArrayIn,0,byteArrayIn.Length);
ms.Write(byteArrayIn, 0, byteArrayIn.Length);
Image returnImage = Image.FromStream(ms,true);
}
catch { }
return returnImage;
}
This is inspired by Holstebroe's answer, plus comments here: Getting an Image object from a byte array
Bitmap newBitmap;
using (MemoryStream memoryStream = new MemoryStream(byteArrayIn))
using (Image newImage = Image.FromStream(memoryStream))
newBitmap = new Bitmap(newImage);
return newBitmap;
Most of the time when this happens it is bad data in the SQL column. This is the proper way to insert into an image column:
INSERT INTO [TableX] (ImgColumn) VALUES (
(SELECT * FROM OPENROWSET(BULK N'C:\....\Picture 010.png', SINGLE_BLOB) as tempimg))
Most people do it incorrectly this way:
INSERT INTO [TableX] (ImgColumn) VALUES ('C:\....\Picture 010.png'))
First Install This Package:
Install-Package SixLabors.ImageSharp -Version 1.0.0-beta0007
[SixLabors.ImageSharp][1]
[1]: https://www.nuget.org/packages/SixLabors.ImageSharp
Then use Below Code For Cast Byte Array To Image :
Image<Rgba32> image = Image.Load(byteArray);
For Get ImageFormat Use Below Code:
IImageFormat format = Image.DetectFormat(byteArray);
For Mutate Image Use Below Code:
image.Mutate(x => x.Resize(new Size(1280, 960)));
I suggest using ImageSharp
Image<Bgra32> image = SixLabors.ImageSharp.Image.LoadPixelData<Bgra32>
(byteArray
, pageWidth
, pageHeight);
I've got to following function which is called to change the resolution of an image. I want to do this so uploaded image with for example 300dpi will be modified to 72dpi (for web). This question is related to another question here on SO where i'm working on.
I'm creation an extension method for this to be able to use this function on more places in my application, instead of only when uploading new files. (See above mentioned question)
public static byte[] SetDpiTo72(this byte[] imageToFit, string mimeType, Size newSize)
{
using (MemoryStream memoryStream = new MemoryStream(), newMemoryStream = new MemoryStream())
{
memoryStream.Write(imageToFit, 0, imageToFit.Length);
var originalImage = new Bitmap(memoryStream);
using (var canvas = Graphics.FromImage(originalImage))
{
canvas.SmoothingMode = SmoothingMode.AntiAlias;
canvas.InterpolationMode = InterpolationMode.HighQualityBicubic;
canvas.PixelOffsetMode = PixelOffsetMode.HighQuality;
canvas.DrawImage((Image)originalImage,0,0, newSize.Width, newSize.Height);
newBitmap.SetResolution(72, 72);
newBitmap.Save(newMemoryStream, ImageFunctions.GetEncoderInfo(mimeType), null);
}
return newMemoryStream.ToArray();
}
}
The mentioned extension methode is being called in a function similar to the situation below;
if (newSize.Width > originalImage.Width && newSize.Height > originalImage.Height)
{
newSize.Width = originalImage.Width;
newSize.Height = originalImage.Height;
uploadedFileBuffer = uploadedFileBuffer.SetDpiTo72(uploadedFile.ContentType, newSize);
return CreateFile(newSize, uploadedFile, uploadedFileBuffer);
}
The bytearray coming in is the file as an bytearray. It already has the correct size, but I want to change the resolution to 72dpi. However after exectution and saving the image the resolution is still the originale entered resolution, which is 300dpi. How can I do this?
UPDATE AFTER SEVERAL ANSWERS:
public static byte[] SetDpiTo72(this byte[] imageToFit, string mimeType, Size newSize)
{
using (MemoryStream memoryStream = new MemoryStream(), newMemoryStream = new MemoryStream())
{
memoryStream.Write(imageToFit, 0, imageToFit.Length);
var originalImage = new Bitmap(memoryStream);
using (var canvas = Graphics.FromImage(originalImage))
{
canvas.SmoothingMode = SmoothingMode.AntiAlias;
canvas.InterpolationMode = InterpolationMode.HighQualityBicubic;
canvas.PixelOffsetMode = PixelOffsetMode.HighQuality;
canvas.DrawImage((Image)originalImage,0,0, newSize.Width, newSize.Height);
originalImage.SetResolution(72, 72);
var epQuality = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, 75);
var epParameters = new EncoderParameters(1);
epParameters.Param[0] = epQuality;
Image newimg = Image.FromStream(memoryStream);
//Getting an GDI+ exception after the execution of this line.
newimg.Save("C:\\test1234.jpg", ImageFunctions.GetEncoderInfo(mimeType), epParameters);
originalImage.Save("test.jpg", ImageFormat.Jpeg);
//This line give me an Argumentexception - Parameter is not valid.
//originalImage.Save(newMemoryStream, ImageFunctions.GetEncoderInfo(mimeType), epParameters);
//newMemoryStream.Close();
}
return newMemoryStream.ToArray();
}
}
The stackstrace which comes with the exception is telling me the following;
at System.Drawing.Image.Save(String filename, ImageCodecInfo encoder, EncoderParameters encoderParams)
at Extensions.ByteArrayExtensions.SetDpiTo72(Byte[] imageToFit, String mimeType, Size newSize) in C:\Website\Project\Extensions\ByteArrayExtensions.cs:line 356
at CMS.Presentation.FileFunctions.CreateFullsizeImage(HttpPostedFileBase uploadedFile, Size newSize, Byte[] uploadedFileBuffer) in C:\Website\Project\CMS.Presentation\FileFunctions.cs:line 197
at CMS.Presentation.FileFunctions.CreateFile(HttpPostedFileBase uploadedFile, INodeService nodeservice, Guid userId, Node parentNode) in C:\Website\Project\CMS.Presentation\FileFunctions.cs:line 53
In the mean time I've also developed another function (see below) resizing just a bitmap. And this seem to work correctly. I can't use this function with my current implementation though because it returns just an Bitmap. Or should i change everything to work with bitmaps?
private static Bitmap ResizeImage(Image image, int width, int height)
{
var frameCount = image.GetFrameCount(new FrameDimension(image.FrameDimensionsList[0]));
var newDimensions = ImageFunctions.GenerateImageDimensions(image.Width, image.Height, width, height);
Bitmap resizedImage;
if (frameCount > 1)
{
//we have a animated GIF
resizedImage = ResizeAnimatedGifImage(image, width, height);
}
else
{
resizedImage = (Bitmap)image.GetThumbnailImage(newDimensions.Width, newDimensions.Height, null, IntPtr.Zero);
}
resizedImage.SetResolution(72,72);
return resizedImage;
}
Ok, I tried it only on files on harddrive, but it should work with streams too.
Bitmap bitmap = new Bitmap(loadFrom);
Bitmap newBitmap = new Bitmap(bitmap);
newBitmap.SetResolution(72, 72);
newBitmap.Save(saveTo);
Took me a while, but I finally found the problem!
The problem lied in the ResizeImage function I used. In the 'GetThumbnailImage' to be specific. I ran into another problem with blurry images, which was explainable because GetThumbnailImage would stretch up the created ThumbNail to the desired size. And the resolution off the thumbnail never changes.
private static Bitmap ResizeImage(Image image, int width, int height)
{
var frameCount = image.GetFrameCount(new FrameDimension(image.FrameDimensionsList[0]));
var newDimensions = ImageFunctions.GenerateImageDimensions(image.Width, image.Height, width, height);
Bitmap resizedImage;
if (frameCount > 1)
{
//we have a animated GIF
resizedImage = ResizeAnimatedGifImage(image, width, height);
}
else
{
resizedImage = (Bitmap)image.GetThumbnailImage(newDimensions.Width, newDimensions.Height, null, IntPtr.Zero);
}
resizedImage.SetResolution(72,72);
return resizedImage;
}
By modifying the function above to the function below I was able to solve the problem using Graphics.DrawImage to redraw the new image before rendering it. Also the GenerateImageDimensions was slightly modified. This taken together the problem was solved.
private static Bitmap ResizeImage(Image image, int width, int height)
{
var frameCount = image.GetFrameCount(new FrameDimension(image.FrameDimensionsList[0]));
var newDimensions = ImageFunctions.GenerateImageDimensions(image.Width, image.Height, width, height);
var resizedImage = new Bitmap(newDimensions.Width, newDimensions.Height);
if (frameCount > 1)
{
//we have a animated GIF
resizedImage = ResizeAnimatedGifImage(image, width, height);
}
else
{
//we have a normal image
using (var gfx = Graphics.FromImage(resizedImage))
{
gfx.SmoothingMode = SmoothingMode.HighQuality;
gfx.InterpolationMode = InterpolationMode.HighQualityBicubic;
gfx.PixelOffsetMode = PixelOffsetMode.HighQuality;
var targRectangle = new Rectangle(0, 0, newDimensions.Width, newDimensions.Height);
var srcRectangle = new Rectangle(0, 0, image.Width, image.Height);
gfx.DrawImage(image, targRectangle, srcRectangle, GraphicsUnit.Pixel);
}
}
return resizedImage;
}
By "changing the resolution", do you actually mean you want to reduce the number of pixels in the image by 72/300? I.e. change a 4000x3000 image to 960x720?
If so, I can't see where your code actually does that. The overload of DrawImage() you're using does this:
Draws the specified image, using its original physical size, at the location specified by a coordinate pair.
Which is exactly what is happening.
Try one of the other overloads such as this one:
Draws the specified Image at the specified location and with the specified size.
for example:
// Create image.
Image newImage = Image.FromFile("SampImag.jpg");
// Create coordinates for upper-left corner of image and for size of image.
int x = 0;
int y = 0;
int width = 450;
int height = 150;
// Draw image to screen.
e.Graphics.DrawImage(newImage, x, y, width, height);
EDIT: per the comments, I understand the OP wants to reduce file size without reducing pixel count. Therefore the files must be recompressed.
I've borrowed some sample code from here:
ImageCodecInfo iciJpegCodec = null;
// This will specify the image quality to the encoder. Change the value of 75 from 0 to 100, where 100 is best quality, but highest file size.
EncoderParameter epQuality = new EncoderParameter(System.Drawing.Imaging.Encoder.Quality, 75);
// Get all image codecs that are available
ImageCodecInfo[] iciCodecs = ImageCodecInfo.GetImageEncoders();
// Store the quality parameter in the list of encoder parameters
EncoderParameters epParameters = new EncoderParameters(1);
epParameters.Param[0] = epQuality;
// Loop through all the image codecs
for (int i = 0; i < iciCodecs.Length; i++)
{
// Until the one that we are interested in is found, which is image/jpeg
if (iciCodecs[i].MimeType == "image/jpeg")
{
iciJpegCodec = iciCodecs[i];
break;
}
}
// Create a new Image object from the current file
Image newImage = Image.FromFile(strFile);
// Get the file information again, this time we want to find out the extension
FileInfo fiPicture = new FileInfo(strFile);
// Save the new file at the selected path with the specified encoder parameters, and reuse the same file name
newImage.Save(outputPath + "\\" + fiPicture.Name, iciJpegCodec, epParameters);
Rob, I believe that issue with your code is at saving the image - the actual digital image data would be certain number of dots/pixels i.e. (m x n) and setting resolution at bitmap wouldn't/shouldn't change the number dots (and hence physical byte size of image). The resolution information will be stored in the image header (to be used by programs while printing/editing images) - what happens if you store the new bitmap to file instead of mem stream
newBitmap.Save("c:\test.png", ImageFormat.Png);
Check dpi for above file from file -> properties -> summary (advanced). It should be 72 dpi.