I am trying to resize a pic of format jpg, reduce it's resolution in order for it to be smaller when I download it to the site HTML. Using the tutorial in the link:
image resizing tutorial
I managed to resize the resolution including cropping when needed. My problem is that actual size of the image got bigger instead of smaller as I expected.
Any ideas please?
If a JPEG image file is getting bigger when you are reducing the dimensions, it's because you are saving it with a higher quality setting than the original.
This is quite normal when you use a compressed image format like jpeg. It is caused by the filter you selected when you reduced the image size. A default selection for the Graphics class, for example, is InterpolationMode.Bilinear. Which does a pretty nice job of making a good looking shrunk version of the image. But at a cost of adding a lot of extra colors to the image due to the filtering algorithm. The resulting image won't compress as well as the original and can in fact require more storage.
You'd have to pick a lower quality filter to avoid this, like InterpolationMode.NearestNeighbor. Yes, won't look nearly as good. In general you should avoid re-compressing an image that was already compressed in a lossy format like jpeg.
Related
My customer has about 100,000 scanned documents (jpg) which they work with everyday. I want to know how can I reduce the file size of those images for faster file transfer and browsing.
The documents are scanned in black/white, saved in jpg format. They have a resolution of 150dpi and size of 1275x1753 (width x height). The main problem is their size which is between ~150kb and ~500kb which I think is too high for a black/white picture.
Is there a chance that I can reduce their size with changing the resolution, changing some color mode or something? Tried playing around with Photoshop but no luck.
The scanned documents are just for the sole purpose of Reviewing. So I don't think they need much detail or the original pic size.
Gonna write the program in c#, So tell me if there is a good image library for this purpose.
If your images are JPEG-compressed than they are either grayscale (8 bits per pixel) or full color (24 or 32 bits per pixel). I am not aware of any other JPEG types out there.
Given that, you probably won't get much benefit if you try to convert these images to other formats without changes to their size (number of pixels in both directions) and/or color space.
There is a possibility that JPEG 2000 might compress your images better than JPEG, but another lossy compression will introduce some more artifacts. You might try for yourself and see if this approach is acceptable for you. I can't recommend you any tools for this approach, though.
I would recommend you to try and convert your images to bilevel ones (i.e. with only two colors) and compress them with one of the FAX compression schemes (Group 3 or Group 4). You might try to reduce images sizes at the same time, too. This can be easily achieved using Docotic.Pdf library (Disclaimer: I work for the vendor of the library).
Please take a look at my answer to a question similar to yours. The answer shows how to use RecompressWithGroup4Fax and/or Scale methods to recompress existing images in PDF.
There is also valuable advice from #plinth about JBIG2 compression and other stuff. Well worth reading.
i am converting 8bpp tif file to 8bpp grayscale but it goes larger in file size. i referred
the following url wischik i have tried atalasoft the file size is fine but the some of the files goes negative in irfanview.
can you guys tell me to solve the above both problem(filesize, negative)?
Images size depends on many factors like bpp, compression, colors..etc
Since you have two tiff 8bpp images I believe the most important factor is the compression since both images will contain palettes.
Ideally in your case the two images should be close in size (memory required) when using the same compression but the colored image will most likely be smaller. I have a sdk called leadtools that I use in my development and it gave me the result above.
Also a small note, maybe if you can provide a sample on the image you are facing the problem with we can help you more.
We have a around 600,000 images that were converted from JPEG to TIFF files and uploaded to our FileNet repository. These TIFF images are multi-page, made by stitching multiple JPEGs.
This was done couple of years ago. Now we started getting complaints from users the quality of the TIFF images are not the same as they were when they were JPEGs.
Is there any way we can improve the quality of TIFF files? If I have to re-migrate this data, can JPEGs be of multiple pages? Please advice.
You can't just add quality to an image, so you can either try improving the appearance of the current information or you'll need to re-create the images to get better information.
To me, it sounds like the initial creation process is the most likely cause of the quality issue. How you create the image is important.
For example, I had a large number of photos I needed to re-size, so I used irfanview's batch convert and the results were horrible. Perhaps I had the settings wrong, I don't know.
I then tried using ImageMagick, and the results were great.
The point being, the conversion process isn't trivial.
If I were you, I'd look at how the images were created, experiment with different settings to determine what gives the best appearance, then re-create your photo gallery.
For photographic material, there's no real reason to use anything other than a jpeg if the target market is the general consumer.
Both TIFF and JPEG support lossless and lossy storage of your images. You mentioned that there was a previous conversion. The conversion was probably a lossy conversion as such you probably won't be able to recover that data to the way it was previously.
That said if you have the original source images you might be able to get back to where you where. Regarding multi-image jpegs, there is such a format *.mpo but I haven't seen it used before so your millage may vary.
You probably converted gray scale or color Jpeg to Tiff. The most common is Tiff G4 which is only 1 bit per pixel. So 24 or 8 bits was converted to 1 bit and you will see a lot of images losses. There are multiple methods to improve image quality but I would have to see the images first to suggest a method.
Goal:
I have lots of pictures in many sizes (both dimensions and file size)
I'd like to convert these files twice:
thumbnail-size pictures
pictures that will look OK on a web page and will be as close to a full screen as possible... and keeping the file size under 500KB.
HTML Questions:
A. What is the best file format to use (jpg, png or other) ?
B. What is the best configuration for web ... as small as possible file size with reasonable quality?
C# Questions
A Is there a good way to achieve this conversion using C# code (if yes, how)?
Try the code in this small C# app for resizing and compressing the graphics. I have reused this code for use in an ASP.NET site without too much work, hopefully you can make use of it. You can run the app to check quality fits your needs etc.
http://blog.bombdefused.com/2010/08/bulk-image-optimizer-in-c-full-source.html
You can pass the image twice, specifying dimensions for a thumbnail, and then again for your display image. It can handle multiple formats (jpg, png, bmp, tiff, gif), and reduce file size significantly without loosing noticeable quality.
On .jpg vs .png, generally jpg is better as you will get a smaller file size than with png. I've generally used this code passing a quality of 90%, which reduces file size significantly, but still looks perfect.
I think PNG is better format for WEB than JPEG that always uses lossy JPG compression, but its degree is selectable, for higher quality and larger files, or lower quality and smaller files. PNG uses ZIP compression which is lossless, and slightly more effective than LZW (slightly smaller files).
In C# you can use System.Drawing namespace types to load, resize and convert mages. This namespace wraps GDI+ API.
A. For graphics I would use png and for fotos jpg.
B. Configuration?
C. There are tons of post that explain that:
http://www.codeproject.com/KB/GDI-plus/imgresizoutperfgdiplus.aspx
Resizing an Image without losing any quality
I'm working on Steganography application. I need to hide a message inside an image file and secure it with a password, with not much difference in the file size. I am using Least Significant Bit algorithm and could do it successfully with BMP files but it does not work with JPEG, PNG or TIFF files. Does this algorithm work with these files at all? Is there a better way to achieve this? Thanks.
This heavily depends on the way the particular image format works. You'll need to dive into the internals of the format you want to use.
For JPEG, you could fiddle with the last bits of the DCT coefficients for each block.
For palette-based files (GIFs, and some PNGs), you could add extra colours to the palette that look identical to the existing ones, and encode information based on which one you use.
You'll have to distinguish between pixel-based (Bitmap) and palette-based formats (GIF) for which the steganographic technique is quite different. Also be aware that there are image formats like JPG that lose information in the compression process.
I'd also advice some general introduction to steganography including different formats.
Least Significant Bit approach does not work with JPEG and GIF images because you are using the pixel data (raw image) to store hidden information before compression. A pixel p, with data 0x123456 will probably not have this value after compression because its value depends on the compression rate and neighbour pixels. In this case we are talking about algorithms that does not only compact the image (like a ZIP, that keeps the content), but changes the color distribution, texture, and quality in order to decrease the number of bits to represent it.
However, PNG can be used just to compact the image in the same sense of ZIP file, keeping the content. Therefore, you can use the Least Significant Bit for PNG images, so that Wikipedia Steganography page shows example in this format.
As long as the image format is lossless, you can use the LSB steganography in pixels (BMP, PNG, TIFF, PPM). If it is lossy, you have to try something else, as compression and subsequent decompression cause small changes in the pixels and the message is gone. In GIF, you can embed your message into the palette. In JPEG you change the DCT coefficients, a low-level frequency representation of the image, which can be read from and saved as JPEG file losslessly.
There is an extensive research on steganography in JPEG. For introduction, I personally recommend Steganography in Digital Media: Principles, Algorithms, and Applications by Jessica Fridrich - must-read material for serious attempts in steganography. The approaches for various image formats are discussed in-depth there.
Also, LSB is inefficient and very easily detectable, you should not use that. There are better algorithms, however usually heavy on math and complex. Look for "steganography embedding distortion" and "steganography codes".