jpeg

问题 I'm trying to load part of big JPEG file (hundreds of megapixels) with a limited memory footprint. I need only about a 1000 scanlines of 20000. It seems that current implementation of libjpeg (as well as its fork libjpeg-turbo) doesn't provide a way to skip unneeded 19k scanlines without decoding them. Is there a workaround for it without digging into libjpeg internals? 回答1: Partial JPEG decoding was implemented in jpeglib-turbo one year ago. I didn't try it, but I guess it should work. Check

问题 <Extension()> _ Public Sub Save(ByVal b As Bitmap, ByVal FileName As String, ByVal Compression As Long, ByVal MimeType As String) Dim Params As EncoderParameters = New EncoderParameters(2) Dim CodecInfo As ImageCodecInfo = GetEncoderInfo(MimeType) Params.Param(0) = New EncoderParameter(Encoder.RenderMethod, EncoderValue.RenderProgressive) Params.Param(1) = New EncoderParameter(Encoder.Quality, Compression) b.Save(FileName, CodecInfo, Params) End Sub this does not work. Its not saved as

问题 I am trying to find a way to read and write JPEG images to user gallery (camera roll) without iOS re-compressing them. UIImage seems to be the bottleneck here. The only method for saving to user gallery I've found is UIImageWriteToSavedPhotosAlbum(). Is there a way around this? For now my routine looks like this –Ask UIImagePickerController for a photo. And when it didFinishPickingMediaWithInfo, do: NSData *imgdata = [NSData dataWithData:UIImageJPEGRepresentation([info objectForKey:@

问题 I know that this question looks like a duplicate but I've followed many online instructions on how to properly install PIL and none have worked. I've tried everything in: Python Image Library fails with message "decoder JPEG not available" - PIL with no success. When I run sudo pip install pil, worst of all, there is a misleading error. Jpeg, Freetyle, etc support is all listed as available. But when running some python code using PIL, the notorious IOError of "decoder jpeg not available'

问题 Has anyone ever had an issue with Loading JPEG files in java? One of our clients is sending files that cannot be resolved, but these same files can be opened in windows. (the other 99% of jpeg files we recieve, process without any problems) I have tried a couple of libraries to read these: itextpdf : com.itextpdf.text.Jpeg (getInstance(imageData) - gives "java.io.IOException: Premature EOF while reading JPG." sanselan : org.apache.sanselan.ImageInfo ( Sanselan.getImageInfo(imageData) gives

问题 ImageIO.read(imagePath) with this file gives a CMMException, why cant Java cope with this seemingly valid file http://www.jthink.net/jaikoz/scratch/front.jpg java.awt.color.CMMException: Invalid image format at sun.awt.color.CMM.checkStatus(Unknown Source) at sun.awt.color.ICC_Transform.<init>(Unknown Source) at java.awt.image.ColorConvertOp.filter(Unknown Source) at com.sun.imageio.plugins.jpeg.JPEGImageReader.acceptPixels(Unknown Source) at com.sun.imageio.plugins.jpeg.JPEGImageReader

问题 I'm currently using the JPGEncoder from the AS3 core lib to encode a bitmap to JPEG var enc:JPGEncoder = new JPGEncoder(90); var jpg:ByteArray = enc.encode(bitmap); Because the bitmap is rather large (3000 x 2000) the encoding takes a long while (about 20 seconds), causing the application to seemingly freeze while encoding. To solve this, I need either: An asynchronous encoder so I can keep updating the screen (with a progress bar or something) while encoding An alternative encoder which is

问题 Is there a theoretical maximum to the amount of metadata (EXIF, etc) that can be incorporated in a JPEG file? I'd like to allocate a buffer that is assured to be sufficient to hold the metadata for any JPEG image without having to parse it myself. 回答1: There is no theoretical maximum, since certain APP markers can be used multiple times (e.g. APP1 is used for both the EXIF header and also the XMP block). Also, there is nothing to prevent multiple comment blocks. In practice the one that is

问题 Is there a theoretical maximum to the amount of metadata (EXIF, etc) that can be incorporated in a JPEG file? I'd like to allocate a buffer that is assured to be sufficient to hold the metadata for any JPEG image without having to parse it myself. 回答1: There is no theoretical maximum, since certain APP markers can be used multiple times (e.g. APP1 is used for both the EXIF header and also the XMP block). Also, there is nothing to prevent multiple comment blocks. In practice the one that is

问题 I'm trying to add a picture (jpeg,png doesn't care) to a plot which is defined by the layout function. For example: a<-c(1,2,3,4,5) b<-c(2,4,8,16,32) m <- matrix(c(1,1,1,1,2,3,2,3), nrow = 2, ncol = 4) layout(m); hist(a);boxplot(a~b);plot(b~a)* Instead of the histogram on position 1 I want to add an image (In my case it's a map) I don't know how to deal with the jpeg package, maybe you can help me! 回答1: You need to read your png or jpeg file through the png and jpeg packages. Then, with the