I have a large PNG that I want uncompressed to a file, but I don't have the memory capacity on the device to expand the PNG in memory, then to a file.
Is there a native iOS method to uncompress a PNG for each scan line? Alternatives?
Libpng - Reading image data - http://www.libpng.org/pub/png/libpng-1.2.5-manual.html#section-3.8
For non-interlaced PNGs
png_read_rows(png_ptr, row_pointers, NULL, number_of_rows);
As and idea how to start:
Take a look how is doing Java the png decompressing algorithm. Java should have open-source those files. Maybe has the iOS too idk. Just get the uncompress algorithm idea. It should be around 1k-5k lines of code.
When you know how to do it, than implement at iOS but read a chunk of file and than export to a file, read another chunk and process and export it. I know it is easy to say and at least theoretically it is working. Maybe is public in some site. Libpng can be a good starting point.
Png is a looseness compression like zip. There as I have remember runtime is built a data table. Those table depends how big is, maybe need to be swapped to to disk, which will makes longer the decompression process.
Good luck!
Related
I have a ID3D11Texture2D and want to write it to disk using literally any picture format (png, bmp, jpeg, ...).
I have already tried to read the docs https://learn.microsoft.com/en-us/windows/win32/api/d3d11/nn-d3d11-id3d11texture2d, which are less than helpful, and i have found an NVIDIA tutorial of how to take individual ID3D11Texture2D and convert them into a video: https://github.com/NVIDIA/video-sdk-samples/tree/master/nvEncDXGIOutputDuplicationSample
However, I dont find anything how to simply write it to disk in any format. I'm sure I'm missing something obvious, any hint would be appreciated.
To experiment, I used https://github.com/NVIDIA/video-sdk-samples/tree/master/nvEncDXGIOutputDuplicationSample, set the frames to capture to 1, and try to write the ID3D11Texture2D to file before encoding to video.
I have a solution for exactly this in the ScreenGrab module which captures a texture (if not already in Map-supporting memory), and then writes it out as a picture using WIC. It handles some edge-cases like "typeless" resources and MSAA as well.
The 'standalone' version is on GitHub here as part of the DirectXTex package:
https://github.com/microsoft/DirectXTex/blob/main/ScreenGrab/ScreenGrab11.h
https://github.com/microsoft/DirectXTex/blob/main/ScreenGrab/ScreenGrab11.cpp
Documentation is here.
ScreenGrab is also included in the DirectX Tool Kit for DX11 and DX12. There's also a basic DX9 version in the DirectXTex package as well.
ScreenGrab can write to any file container supported by WIC. It also has buit-in support for writing DDS files directly without using WIC.
In addition to using ScreenGrab (which is intended as a light-weight screenshot solution), you can also use the DirectTex library to capture a texture and then save it to DDS, HDR, TGA, or any WIC-supported file format.
I'm writing a mod for a game that uses lua/luajit as a scripting language and I would like to create a png file dynamically using lua. I've been googling for a png library/module but could only find ones that merely read pngs (like https://github.com/Didericis/png-lua or https://luapower.com/libpng), or create uncompressed pngs: https://github.com/wyozi/lua-pngencoder
On my search I have stumbled upon libpng and thought, maybe I could simply load that dll using ffi and use the functions that way. But the problem is that is waaaay too complicated for me, since I'm not familiar with C and furthermore libpng seems to be a huuuuuge complicated library.
So, is there any simple way (module/library) that I missed and didn't find on google?
I just need very simple functionality, create a png, set the pixels, save it as a compressed png file.
I like to convert an .jpg or .png file to an .svg format that can be displayed in UIImageView. Is there a way to do this in Objective-C?
You shouldn't use SVG images in Xcode:
it is recommended that you use PNG or JPEG files for most images in your app. Image objects are optimized for reading and displaying both formats, and those formats offer better performance than most other image formats. Because the PNG format is lossless, it is especially recommended for the images you use in your app’s interface.
Also, there's an SVGKit that according to many devs is buggy so use it at your own risk.
SVG is an XML-based vector and in Xcode you can also use vectors but using a PDF format and follow this tutorial.
In a nutshell:
Generate PDFs With the #1x Asset (During compile time it will generate #2 and #3)
Set the Scale Factors to Single Vector:
Drag and Drop Your PDF Into the All, Universal Section
Refer to Your Image by Its Name, Like for any PNG File
[UIImage imageNamed:#”Home”]
Also, stackoverflow (perhaps) related answer
To convert PNG to SVG (Which is a very sensible and valid thing to do) you need an app or library called a "tracer". It will trace the outlines of shapes, gradients, etc and convert them into vector representations.
For simple cases, this is easy for a computer to do; for complex cases (e.g. gradients), this is a very hard AI / Computer-Vision problem and you'd need to spend $$$ on high-end coding solutions and/or find PhD-level research that solves the problem!
A free tracer that does a very good job is built-in to Inkscape (open-source) - google "inkscape trace" for tutorials on how to use it, and to generate a .svg file that you can use. This is a manual process.
To use this in-app, you need to find a tracing library for iOS. The libraries that Inkscape uses are all open-source, so you could try converting them to iOS - they're written in C, so it could be quite easy.
I am working a kids app. It has number of video files and png files. All to gather came to size of 1.6GB after compressing. Is there any way to reduce the file size to use in app.
try compress your image resources.
imageOptim is good choice.
some kind of unnecessary resources, you can make it to download. Video always the hard-disk space killer, put it in the server, if you want to display it, request it and download it as cache.
I tried looking through the libpng documentation, but didn't find what I was looking for.
I have a PNG file fully in a memory buffer, how can I load this file (apart from the obvious solution of creating a temporary file)?
Not sure if it's relevant, but I'm calling libpng from Python using ctypes.
I found this article which describes pretty well how to read a PNG file from memory.
Summarized, you have to create a custom callback function and give it to libpng using png_set_read_fn. Then in that callback function you read from your memory buffer rather than a file.