I found a solution now, that works, at least if my resulting image is also a JPEG: First I read the image (from byte array imageData), and most important, I also read the metadata. InputStream is = new BufferedInputStream(new ByteArrayInputStream(imageData)); Image src = null; Iterator<ImageReader> it = ImageIO.getImageReadersByMIMEType(“image/jpeg”); ImageReader reader = it.next(); ImageInputStream iis = … Read more
You could use the <picture> element to deliver a WebP image to users with browsers that support it, falling back to a JPEG or PNG for those that don’t. The advantage of using the <picture> element rather than other fallback methods is that browsers that don’t support the element will fallback to whatever source is … Read more
It is probably due to some wrong wrapping of the imwrite() parameters from Python to C, cv2.IMWRITE_JPEG_QUALITY (which is of type “long”), and causes some weird problems. You should try to convert this constant to “int” type: cv2.imwrite(‘img_CV2_90.jpg’, a, [int(cv2.IMWRITE_JPEG_QUALITY), 90]) for me it solved the problem (python 2.7.2, opencv 2.4.1)
The compressed data will not include SOI or EOI bytes, so you are safe there. But the comment, application data, or other headers might. Fortunately, you can identify and skip these sections as the length is given. The JPEG specification tells you what you need: http://www.w3.org/Graphics/JPEG/itu-t81.pdf Look at Table B.1, on page 32. The symbols … Read more
From wikipedia: JPEG image files begin with FF D8 and end with FF D9. http://en.wikipedia.org/wiki/Magic_number_(programming)
The ImageMagik command: identify -format ‘%[channels]’ foo.png will print rgba or rgb if there is or is not an alpha channel, respectively. There could be an alpha channel present with no data in it which wouldn’t actually have any transparency, but that is a bit more complicated.
Several options: You can check for the file extension: static bool HasJpegExtension(string filename) { // add other possible extensions here return Path.GetExtension(filename).Equals(“.jpg”, StringComparison.InvariantCultureIgnoreCase) || Path.GetExtension(filename).Equals(“.jpeg”, StringComparison.InvariantCultureIgnoreCase); } or check for the correct magic number in the header of the file: static bool HasJpegHeader(string filename) { using (BinaryReader br = new BinaryReader(File.Open(filename, FileMode.Open, FileAccess.Read))) { UInt16 … Read more
To read metadata/EXIF from image byte[] (useful for Camera.takePicture()) using version 2.9.1 of the metadata extraction library in Java by Drew Noakes: try { // Extract metadata. Metadata metadata = ImageMetadataReader.readMetadata(new BufferedInputStream(new ByteArrayInputStream(imageData)), imageData.length); // Log each directory. for(Directory directory : metadata.getDirectories()) { Log.d(“LOG”, “Directory: ” + directory.getName()); // Log all errors. for(String error : … Read more
I was receiving the same error message. I then installed gs and the same command worked properly after that.
Ok, I know that you did already solve your problem, but as some people, just like me, could be searching some simple example I will share what I created. It is an example, compressing and decompressing an RGB image. Otherwise I think that the API documentation of TurboJPEG is quite easy to understand! Compression: #include … Read more