I'm writing a service for a project that's going to handle our image processing. One such process is supposed to strip all metadata from the byte[] provided and return the same image as a byte[].
The method I'm currently working on involves always converting the image to a Bitmap, then converting it back to the original format and returning the data from a MemoryStream.
I haven't been able to test it yet but something tells me I'm going to experience some quality loss.
How can I remove all metadata from any image with a common format?
(bmp, gif, png, jpg, icon, tiff)
Not sure how I can narrow that down any further. Would be nice if I got some feedback regarding the downvotes.
For the lossless formats (except JPEG), your idea of loading it as a bitmap and re-saving is fine. Not sure if .NET natively supports TIFFs (I doubt it does).
For JPEGs, as you suggested there may be quality loss if you're re-compressing the file after decompressing it. For that, you might try the ExifLibrary and see if that has anything. If not, there are command line tools (like ImageMagick) that can strip metadata. (If you use ImageMagick, you're all set, since it supports all of your required formats. The command you want is convert -strip.)
For TIFFs, .NET has built-in TiffBitmapDecoder and ...Encoder classes you might be able to use; see here.
In short, using an external tool like ImageMagick is definitely the easiest solution. If you can't use an external tool, you're almost certainly going to need to special-case the formats that .NET doesn't support natively (and the lossy JPEG).
EDIT: I just read that ImageMagick doesn't do lossless stripping with JPEGs, sorry. I guess using the library I linked above, or some other JPEG library, is the best I can think of.
Related
There are several SO posts and googling which did not really help much with my question. So here I go again.
I need to convert a PDF to a single tiff image (multi-page tiff obviously). I have figured out the tiff creation part. But the issue is with extracting a image/bitmap from pdf. Of course c# .net does not have the functions, but there should be way to do it.
On why I dont want to use third party libraries, its because they are not free - some may be, but for security reasons it may not be usable in all environments. And more than everything just curious how to do it and in some posts this question is being treated as a sin :).
Any proper methods/ideas or where to start would be helpful. I would prefer WPF based solutions than GDI+ based, as I have seen issues with GDI+ tiff creation solution on windows servers . I was of the idea that creating pdf is more difficult and of course I can understand if it was easy it should have been in .net already.
Edit: Also for a starter, a pdf which contains a simple format would be nice. Not necessary that it should support every type of pdf.
Even with 3rd party it's not going to be easy :) Convert a PDF into a series of images using C# and GhostScript
I have problem with image compression. I need to compres a lot of files (700-900kb) to files 70-80kb without
loss of quality. (or small loss ) I found menu item "Save for Web & Devices ..." in Photoshop. It works great.
But I don't want to use photoshop programmatically. May be someone knows how to solve this problem with
other third party components or frameworks?
Thanks for any ideas!
.NET has a number of image decoding/encoding libraries, often tied to a particular GUI framework (e.g. in Windows Forms you have System.Drawing.Image and for WPF, see the Imaging Overview chapter on msdn).
There are also third party libraries specialized in image conversion/compression that you can find online (both free and non free)
Generally though, the amount of saving you get from compressing an image highly depends on the original format. If you already have JPEG photos with normal compression (quality of 85%) then there is not much you can do in terms of making them smaller except resizing them. If you have raw bitmaps (e.g. BMP, uncompressed/low compression TIFF etc.) then you can expect quite large savings with most compressing formats
When choosing image format, consider this:
Photos and similar: JPEG will often do fine. Good savings with reasonable quality loss
Screenshots and similar: PNG will generally give best results (PNG is lossless). JPEG will often create highly visible artifacts on screenshots
Compressing an already compressed image (i.e. PNG, JPEG etc.) with a general purpose compression algorithm like ZIP or RAR will in practice not give you any savings. You may actually end up with a bigger file.
You can have a look at the FreeImage project. It has a C# wrapper that you can use.
Imagemagick allows you to batch-processing on files and offers a everything you could possible ask for when it comes to handling of images
E.g. to resize every image in folder (destroy originals) to QVGA do
mogrify -resize 320x240 *.jpg
To preserve aspect ratio do
mogrify -resize 320x240! *.jpg
If you need to traverse a directory structure, this is how you can do it in *nix based systems (also destroying originals)
find . -type f -name *.jpg -exec convert -resize 800x800 {} \;
There is also an quality switch available, see here
I'm writing a method that needs to save a System.Drawing.Image to a file. Without knowing the original file the Image was created from, is there anyway to determine what file extension it should have?
The best solution I've come up with is to use a Switch/Case statement with the value of Image.RawFormat.
Does it even matter that I save the Image in it's original format? Is an Image generated from a PNG any different from say one generated from a JPEG? Or is the data stored in an Image object completely generic?
While Steve Danner is correct in that an image created from a JPG will look different to an image created from a PNG once it's loaded into memory it's an uncompressed data stream.
This means that you can save it out to any file format you want.
However, if you load a JPG image and then save it as another JPG you are throwing away more information due to the compression algorithm. If you do this repeatedly you will eventually lose the image.
If you can I'd recommend always saving as PNG.
Image.RawFormat has cooties, stay away from it. I've seen several reports of it having no legal value for no apparent reason. Undiagnosed as yet.
You are quite right, it doesn't matter what format you save it to. After you loaded the file, the internal format is the same for any bitmap (not vector) with the same pixel format. Generally avoid recompressing jpeg files, they tend to get bigger and acquire more artifacts. Steve mentions multi-frame files, they need to be saved a different way.
Yes, it definitely matters because different fileformats support different features such as compression, multiple frames, etc.
I've always used a switch statement like you have, perhaps baked into an extension method or something.
To answer your question 'Does it even matter that I save the Image in it's original format?' explicitly: Yes, it does, but in a negative way.
When you load the image, it is uncompressed internally to a bitmap (or as ChrisF calls it, an uncompressed data stream). So if the original image used a lossy compression (for example jpeg), saving it in the same format will again result in loss of information (i.e. more artifacts, less detail, lower quality). Especially if you have repeated actions of read - modify - save, this is something to avoid.
(Note that it is also something to avoid if you are not modifying the picture. Just the repeated decompress - compress cycles will degrade the image quality).
So if disk space is not an issue here (and it usually isn't in the age of hard disks that are big enough for HD video), always store any intermediate pictures in lossless compression formats, or uncompressed. You may consider saving the finall output in a compressed format, depending on what you use it for. (If you want to present those final pictures on the web, jpeg or png would be good choices).
I'm having issues with TIFFs
Here is what I have to do, we have tiff images saved into the database, these images are CCITT4 compressed with a number of required tags, these include:
RowsPerStrip must be the ImageLength
Photometric Interpreation must be MinIsWhite
Multi-strip image format is not allowed
My problem is, I'm using the built in System.Drawing.Bitmap/Image objects, which happen to change the values of these when I put it into the object, I've tested this by saving the byte[] to a tiff directly from the database, checked the tags, they are fine.. but when i put the bytes into an Image object then save to file, they are modified.
To make things worse, I'm needing to add a text to the image before saving it.
So I need a component that will allow me more control with TIFF (and they must be tiff), and be able to add text to an image or be able to use the Graphics object.
I've tried using LibTiff but I have yet to see any examples on how to use this component,
any suggestions?
You can use our free and open-source LibTiff.Net library for this. It is freely available for all uses under a BSD license. The just released version 2.0 contains good documentation and number of samples.
There are samples that show how to convert any non-tiled TIFF image to the TIFF image which have all data written in a single strip and how to convert a System.Drawing.Bitmap to 1-bit CCITT single strip TIFF image.
I have never used the built int System.Drawing.Bitmap objects to do this. I personally use LeadTools, but it isn't free. It is however a robust and fairly straightforward API. I primarily use it for GEOTiff which contain specific data tags for image location data.
There is a 60 day evaluation if you would like to try it out.
I use FreeImage. There's a C# .NET wrapper available too.
The IEvolution component set from HiComponents is now totally free (no source) - http://www.hicomponents.com. A very powerful .NET imaging toolkit.
Is it possible to load and display EPS file using plain WinForms GDI+? If not, is there a free library to help out?
I seem to remember that Windows GDI supported EPS files, but after Googling around a bit, I am starting to doubt that memory.
All I want to do is load the file and draw it using a Graphics context.
I am aware that I can just use any program to convert the file to PNG or something and render it that way, but because I am trying to render at multiple resolutions, I would prefer to keep the vector data in the EPS file.
Thanks!
All the free or open source libraries I know that can convert EPS to other vector or raster format are all based on Ghostscript. You can invoke ghostscript directly, with wrapper provided or alternatively look at imagemagick. It is a very popular library for manipulating image graphics and has been around for a long time. It also internally relies on Ghostscript for handling EPS format. There is a .NET wrapper for it that you can find at http://imagemagick.codeplex.com/. You can read a bit about its background here too http://www.codeproject.com/KB/dotnet/ImageMagick_in_VBNET.aspx. There is also pstoedit that is also based on ghostscript to read EPS and allow export to format like WMF. You will need to the call to pstoedit API using interop in .NET
Besides Ghostscript there are several commercial products that I known of like ImageGear and LeadTools which will let you take EPS to almost any other kind of graphic formats.
You can use GhostScript to produce images from an EPS. Once you have an image you can then display that within your application.
In your question you indicated you want the output in a vector format which would preclude bitmaps, jpeg etc. Here are a couple of ways of getting a XAML file which is a vector file with extensive support by Microsoft.
Microsoft Expression Blend 3 and Design 3 can both open .ai (eps) files and convert them to vector formats, design and XAML respectively, so it is definitely possible.
I know it is relatively easy to automate most Microsoft Office applications like Word and Excel, but I have not seen any documented com inter-op assemblies for these Expression products.
Perhaps you can use the converters that are part of Expression in an undocumented way?
If that doesn't work here is plan B:
Here is a free converter that will convert .ai (eps) files to XAML. To use it you need Adobe Illustrator however.