I'm trying to figure out what is the best way to "clean" images that are coming from non authorized source (app visitors) before opening them, similar to Whatsapp.
Scanning each image with anti virus is probably not so efficient in a large scale, So i came to assumption that rewriting each incoming image by compressing it using jpeg could results a clean image without a malicous code inside it.
From what i read so far the JPEG compression should destroy any hidden content and reorder the data structure of the image which will results a safe image.
WTYT? Am i on the right path to overcome this issue?
There is no code in a JPEG stream. In fact, I don't know of any image format that directs the decoder execute code.
The worst think I can thing of would be to have a JPEG stream that, say embedded malicious code in a thumbnail, COM, or APPn marker. Then another application would look for that image and load the code.
Even this requires something else to get on your system to execute the JPEG "code" and it would be a lot of trouble for something that could be accomplished much easier.
I'm trying to load images in WebGL, and then uploading them to the GPU. I'd like to use a compressed texture format, even though the original images are uncompressed/lossless.
To upload, this is what I'm doing:
gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA, gl.UNSIGNED_BYTE, textureSource);
In the above code, textureSource is a loaded (say, "texture.png").
It all works well, but I'd like to load WEBGL_compressed_texture_s3tc formats (COMPRESSED_RGB_S3TC_DXT1_EXT) to store the image in a compressed fashion.
I make sure that the extension is available and enabled...
var ext = gl.getExtension("WEBGL_compressed_texture_s3tc");
var fmt = ext.COMPRESSED_RGBA_S3TC_DXT5_EXT;
console.log(fmt); // 33779
But then I can't use it as a format. Using texImage2D() doesn't work:
gl.texImage2D(gl.TEXTURE_2D, 0, fmt, fmt, gl.UNSIGNED_BYTE, textureSource);
// WebGL: INVALID_ENUM: texImage2D: invalid texture format
// [.WebGLRenderingContext]RENDER WARNING: texture bound to texture unit 0 is not renderable. It maybe non-power-of-2 and have incompatible texture filtering or is not 'texture complete'
The expected method is compressedTexImage2D(), but that's not very helpful either:
gl.compressedTexImage2D(gl.TEXTURE_2D, 0, fmt, 256, 256, 0, texture.source);
// Uncaught TypeError: Failed to execute 'compressedTexImage2D' on 'WebGLRenderingContext': parameter 7 is not of type 'ArrayBufferView'.
This is obviously because compressedTexImage2D() expects an Uint8Array with the actual DDS/DXT data, not a JavaScript image like what I'm passing.
The obvious solution is to uploading files in their native DDS format - files that have been compressed somewhere else. But that's what I'm trying to avoid: in my current workflow, it'd make sense to have the image in their original format rather than pre-compress them (or having duplicates).
My question then is as such: can I still use the original PNG images, loading them, and having them upload to the GPU on their compressed format? In other words, can I compress textures to their DXT1/5 formats on the fly?
I'm a little bit constrained by video memory in what I'm doing, so any saving would be great. I managed to minimize the space used by the textures by using UNSIGNED_SHORT_4_4_4_4 and the other data types, which is a good start, but I'd like to try using the native compression too.
I haven't found much documentation on the topic, nor found relevant code on other popular libraries (Three.js, Pixi, etc), which leads me to believe that my request is super stupid, but I'd like to understand why. This page hints at licensing issues, which might be why WebGL doesn't feature a way to properly compress the file, nor allow for browser support of image objects.
can I still use the original PNG images, loading them, and having them upload to the GPU on their compressed format? In other words, can I compress textures to their DXT1/5 formats on the fly?
As far as I am informed: NO.
I only work on desktop and embedded GL, but even there is no chance to compress textures on the fly without dedicated code or a library.
(And, well, those DXT formats are not very good, either, if your textures are too detailed or have lots of different colors within small buckets. Most likely you're better off just using smaller textures, as the DXT1 compresses to 1/8th and DXT5 to 1/4 of the original size (which is like halving the resolution of the texture).)
Theoretically I think you could compress the PNGs to DXT with Javascript. I guess that'd be just mad though :)
Better encode beforehand with native code. An option for supporting PNG content is to have an asset proxy for doing the conversions on the fly on server side (our partner company that hosts http://www.meshmoon.com/ does exactly that).
Using the Quartz 2D PDF routines, can the CGPDFDataFormat format of a CGPDFStreamRef PDF stream be equal to CGPDFDataFormatJPEG2000 in any case other than for an XObject image with a filter of /JPXDecode?
In other words, is the CGPDFDataFormatJPEG2000 format ever used for anything other than JPEG2000 image streams? The reasonable answer would be no, but there can always be a difference between common usage and what's theoretically possible.
JPXDecode filter expects a JPEG2000 image file to be stored in the image XObject, not just compressed raw data. I can say 100% it is always used for image XObjects. But theoretically nothing stops you to wrap your raw content stream data as a JPEG2000 image and then use the JPXDecode filter with a regular content stream. It is just not practical.
I'm using CameraCaptureTask chooser and always is returning a smaller photo that the original. Camera has a resolution of 2592x1944, but the returned photo is always 1296x972. I'm using a LG E-900.
Any ideas ?
Any JPG or PNG image file that is loaded into a BitmapImage object on Windows Phone will automatically be re-sized to be less than 2000x2000 to reduce the internal memory used to display the image to the screen. If you must access the image at a higher resolution you will need access to the original byte stream (e.ChosenPhoto from the completed event for example) and then load that into a System.Windows.Media.Imaging.WriteableBitmap object.
The issue then becomes that you may need to know the original size of the image, as the WriteableBitmap takes a size and width as part of it's constructor and will automatically re-size the image that you try and load into it. I believe the only way to load a high resolution image at it's original size is to use ExifLib on the byte stream to detect the original height and width, then create a WriteableBitmap at that size and use the System.Windows.Media.Imaging - Extensions.LoadJpeg method to load the image into the object. For more image loading samples see this question regarding re-sizing an image on Windows Phone.
Sorry - but there's currently no way to do this - see Is it possible to configure the resolution of `CameraCaptureTask` in WP7?
if you are lucky, then the new Mango SDK might help - it's now 2 weeks away.
I've got a handle to a BITMAP structure (HBITMAP) in a Windows Mobile application -- I'd like to save the bitmap as a PNG file, using the IImage interface if possible. (There's no BMP file in this situation, the BITMAP is only in memory).
It looks like I could use IImagingFactory's IImagingFactory::CreateImageEncoderToFile method to save the file but I think I'd first have to get the BITMAP converted into "IImage" format.
Any ideas on how to do this with native code?
Use CreateImageFromStream to read in your BITMAP data, that gives you an IImage.
Edit:
I did a little more research on this. There are a couple paths, but I think the easiest is to:
create a DIBSECTION and blit your bitmap to it.
Create a BitmapData instance pointing to the DIBSECTION for the image data.
Call CreateBitmapFromBuffer to generate an IBitmapImage interface
Push the IBitmapImage (which is an IImage) through your encoder.