文件列表:

LICENSE (1065, 2023-07-22)
UPNG.js (47731, 2023-07-22)
package.json (577, 2023-07-22)

# UPNG.js A small, fast and advanced PNG / APNG encoder and decoder. It is the main PNG engine for [Photopea image editor](https://www.photopea.com). * [Examples of PNGs minified by UPNG.js](https://blog.photopea.com/png-minifier-inside-photopea.html#examples) * [Try UPNG.js in Photopea](https://www.photopea.com) - open an image and press File - Save for web, play with the Quality * [UPNG.Photopea.com](http://upng.photopea.com) - a separate minifier app, that uses UPNG.js * Support us by [making a donation](https://www.paypal.com/cgi-bin/webscr?cmd=_donations&business=ivan%40kuckir%2ecom&lc=CZ&item_name=UPNG%2ejs¤cy_code=USD&bn=PP%2dDonationsBF%3abtn_donateCC_LG%2egif%3aNonHosted). Download and include the `UPNG.js` file in your code. ## Encoder UPNG.js supports APNG and the interface expects "frames". Regular PNG is just a single-frame animation (single-item array). #### `UPNG.encode(imgs, w, h, cnum, [dels])` * `imgs`: array of frames. A frame is an ArrayBuffer containing the pixel data (RGBA, 8 bits per channel) * `w`, `h` : width and height of the image * `cnum`: number of colors in the result; 0: all colors (lossless PNG) * `dels`: array of millisecond delays for each frame (only when 2 or more frames) * returns an ArrayBuffer with binary data of a PNG file UPNG.js can do a lossy minification of PNG files, similar to [TinyPNG](https://tinypng.com/) and other tools. It performed quantization with [k-means algorithm](https://en.wikipedia.org/wiki/K-means_clustering) in the past, but now we use [K-d trees](https://en.wikipedia.org/wiki/K-d_tree). Lossy compression is allowed by the last parameter `cnum`. Set it to zero for a lossless compression, or write the number of allowed colors in the image. Smaller values produce smaller files. **Or just use 0 for lossless / 256 for lossy.** // Read RGBA from canvas and encode with UPNG var dta = ctx.getImageData(0,0,200,300).data; // ctx is Context2D of a Canvas // dta = new Uint8Array(200 * 300 * 4); // or generate pixels manually var png = UPNG.encode([dta.buffer], 200, 300, 0); console.log(new Uint8Array(png)); #### `UPNG.encodeLL(imgs, w, h, cc, ac, depth, [dels])` - low-level encode * `imgs`: array of frames. A frame is an ArrayBuffer containing the pixel data (corresponding to following parameters) * `w`, `h` : width and height of the image * `cc`, `ac`: number of color channels (1 or 3) and alpha channels (0 or 1) * `depth`: bit depth of pixel data (1, 2, 4, 8, 16) * `dels`: array of millisecond delays for each frame (only when 2 or more frames) * returns an ArrayBuffer with binary data of a PNG file This function does not do any optimizations, it just stores what you give it. There are two cases when it is useful: * saving 16-bit colors (note, that PNG is big-endian, unlike Uint16Array in JS) * your image is too large, and "expanding" to 8-bit RGBA would use too much memory (e.g. 4-bit grayscale 50,000 x 50,000 = 1.25 GB, 8-bit RGBA would be 10 GB) ## Decoder Supports all color types (including Grayscale and Palettes), all channel depths (1, 2, 4, 8, 16), interlaced images etc. Opens PNGs which other libraries can not open (tested with [PngSuite](http://www.schaik.com/pngsuite/)). #### `UPNG.decode(buffer)` * `buffer`: ArrayBuffer containing the PNG file * returns an image object with following properties: * * `width`: the width of the image * * `height`: the height of the image * * `depth`: number of bits per channel * * `ctype`: color type of the file (Truecolor, Grayscale, Palette ...) * * `frames`: additional info about frames (frame delays etc.) * * `tabs`: additional chunks of the PNG file * * `data`: pixel data of the image PNG files may have a various number of channels and a various color depth. The interpretation of `data` depends on the current color type and color depth (see the [PNG specification](https://www.w3.org/TR/PNG/)). #### `UPNG.toRGBA8(img)` * `img`: PNG image object (returned by UPNG.decode()) * returns an array of frames. A frame is ArrayBuffer of the image in RGBA format, 8 bits per channel. ### Example var img = UPNG.decode(buff); // put ArrayBuffer of the PNG file into UPNG.decode var rgba = UPNG.toRGBA8(img)[0]; // UPNG.toRGBA8 returns array of frames, size: width * height * 4 bytes. PNG format uses the Inflate algorithm. Right now, UPNG.js calls [Pako.js](https://github.com/nodeca/pako) for the Inflate and Deflate method. ## Quantizer UPNG.js contains a very good Quantizer of 4-component 8-bit vectors (i.e. pixels). It can be used to generate nice color palettes (e.g. Photopea uses UPNG.js to make palettes for GIF images). Quantization consists of two important steps: Finding a nice palette and Finding the closest color in the palette for each sample (non-trivial for large palettes). UPNG perfroms both steps. var res = UPNG.quantize(data, psize); * `data`: ArrayBuffer of samples (byte length is a multiple of four) * `psize` : Palette size (how many colors you want to have) The result object "res" has following properties: * `abuf`: ArrayBuffer corresponding to `data`, where colors are remapped by a palette * `inds`: Uint8Array : the index of a color for each sample (only when `psize`<=256) * `plte`: Array : the Palette - a list of colors, `plte[i].est.q` and `plte[i].est.rgba` is the color value ### FAQ - To get one common palette for multiple images (e.g. frames of the animation), concatenate them into one array `data`. - When working with less than four components, set the remaining components to a constant value (e.g. to zero) - When working with transparency, premultiply color components by transparency (otherwise, rgba(1,1,1,0) would be closer to rgba(1,1,1,1) than to rgba(0,0,0,0) - transparent mapped to white instead of transparent)

近期下载者：

相关文件：

评论：[我要评论] [举报此文件]

收藏者：