I am working on an iOS application that does some image processing.
The result of the processing is a grey-scale image.
When the process is finished, I want to save the original RGB image together with the result in a same image file to camera roll, so I thought of using alpha channel for that.
Also, I want to attach some parameters got in the processing as image metadata.
So here it comes my problem. I could not find an iOS compatible image format that allows saving alpha channel together with metadata.
On the one hand, JPEG images accept metadata, but not alpha channel.
On the other hand, PNG images accept alpha channel, but not metadata.
Any ideas?
Thanks in advance.
On the other hand, PNG images accept alpha channel, but not metadata.
But yes metadata.
Related
This is very basic requirement but did not get any result after research. In Swift 3.0, by using below API, we have saved captured image.
UIImageWriteToSavedPhotosAlbum
UIImage object have the image. Basic way to send image to server is convert the UIImage to NSData. To perform this below two API are available.
UIImageJPEGRepresentation //NOTE - We must specify the compression parameter.
UIImagePNGRepresentation // We don't need to specify the compression parameter.
By default, image saved is in JPEG format, we want to send SAME image to server WITHOUT any compression.
So size of jpeg image in album and size of image on server must be exactly same.
How do I achieve this ?
Thank you for help.
I am updating some textures of the scene all the time by new images.
Problem is uploading is synchronous and texImage2D takes ~100ms. It takes so long time even if texture is not used during rendering of the next frame or rendering is switched off.
I am wondering, is there any way to upload texture data asynchronously?
Additional conditions:
I had mention there is old texture which could stay active until uploading of new one to GPU will be finished.
Solution is to use texSubImage2D and upload image to GPU by small portions. Once uploading will be finished activate your new texture and delete old one.
is there any way to upload texture data asynchronously?
no, not in WebGL 1.0. There might be in WebGL 2.0 but that's not out yet.
Somethings you might try.
make it smaller
What are you uploading? Video? Can you make it smaller?
Have you tried different formats?
WebGL converts from whatever format the image is stored in to the format you request. So for example if you load a .JPG the browser might make an RGB image. If you then upload it with gl.RGBA, gl.RGBA, gl.UNSIGNED_BYTE it has to convert the image to RGBA before uploading (more time).
Do you have UNPACK_FLIP_Y set to true?
If so WebGL has to flip your image before uploading it.
Do you have UNPACK_COLORSPACE_CONVERSION_WEBGL set to BROWSER_DEFAULT_WEBGL?
If not WebGL may have to re-decompress your image
Do you have UNPACK_PREMULTIPLY_ALPHA_WEBGL set to false or true?
Depending on how the browser normally stores images it might have
to convert the image to the format your requesting
Images have to be decompressed
are you sure your time is in "uploading" vs "decompressing"? If you switch to uploading a TypedArray of the same dimensions does it speed up?
In my app, I convert and process images.
from colour to greyscale, then doing operations such as histogram-equalisation, filtering, etc.
that part works fine.
my UIImage display correctly, I also save them to jpeg files and it works.
The only problem is that, although my images are now greyscales, they are still saved as RGB jpegs. that is the red, green and blue value for each pixel are the same but it still waste space to keep the duplicated value, making the file size higher than it could be.
So when i open the image file in photoshop, it is black & white but when I check "Photoshop > Image > Mode", it still says "RGB" instead of "Greyscale".
Anyone know how to tell iOS that the UIImageJPEGRepresentation call should create data with one channel per pixel instead of 4?
Thanks in advance.
You should do an explicit conversion of your image using CGColorSpaceCreateDeviceGray() as color space which is 8 bits per component, 1 channel.
I'm capturing an image from the iPhone camera and storing it in the document folder for further check and use.
Before storing the image i want to check the image quality based on the RGB value, grayscale and white balance , etc.
All that i can get from the image. But i am not able to understand what should or how should i use any framework that would help me retrieve this information.
Any help would be appreciated.
Thank you!
This app may do what you want. It is called Photo Metadata Reader. I saw it had RGB in the screenshots.
https://itunes.apple.com/us/app/photo-metadata-reader/id437865801?mt=8
If you want to retrieve metadata from UIImage - check this
https://github.com/foundry/UIImageMetadata
If you want to get, for example, color balance, I think you must get pixel data from image and compute this by yourself
I need to edit a png image,by giving it border and drop shadow effect. But the final size of the edited image is too high to use for a mobile app .I know that size of jpeg is less compared to that of png.So i convert that image to jpeg and tried to give drop shadow and border effect.But that image is not having transparent background..Is their any other methods to accomplish this using jpeg?
Another option is to try either ImageOptim for losseless compression, or its lossy cousin, ImageAlpha.
ImageOptim tries a series of lossless algorithms to shrink a PNG and selects the smallest result of the bunch. It has taken 25% to 50%+ of quite a few of our images.
ImageAlpha, on the other hand, is lossy and can further crunch the image, with results more like JPEG but without losing Alpha.
You would also do well to disable PNG compression in Xcode as shown here, with additional details here.
What #minitech wanted to say is not about scaling, it's about file compression. jpg and png files usually have some data that could be removed from the file. There are some compression methods to reduce file size (note that is size in kbs, not in scale measurement). Jpg images can reduce file size by reducing image quality, too.
If you want another file type that accepts transparency, there are the gif format, which gives you a smaller file, but have some drawbacks, like a lack of alpha channel (variable transparency). Check this link for more details: http://www.w3.org/QA/Tips/png-gif
There are a couple of online file compressors. If you want to compress png files, you could try using http://tinypng.org/
No, jpeg image wont support transparency.But you can change the white background coming along with jpeg image