mitasovr / png-img

Lite libpng wrapper for node.js

png-img

Liteweight png image processing library.

Note: since v2.0.0 this lib based on pngjs2 and doesn't build any native modules.

Installation

npm install png-img

API

PngImg.fromBuffer(buffer, cb)

Create PngImg object from passed buffer with image.

Arguments:

• buf - Buffer with image file content
• cb - callback. Will be called when image will be parsed

var fs = require('fs'),
    PngImg = require('png-img');

var buf = fs.readFileSync('path/to/img.png');

PngImg.fromBuffer(buf, function(err, img) {
  if (err) {
    console.error(err);
  } else {
    // Use `img`
  }
});

size()

Get image size as an object.

console.log(img.size());

for 32x32 image will print out:

{ width: 32, height: 32 }

get(x, y)

Get pixel color and alpha.

Returns object:

• r: red channel (0 to 255)
• g: green channel (0 to 255)
• b: blue channel (0 to 255)
• a: alpha (0 to 255). 0 - transparent

console.log(img.get(0, 0));

will print pixel and color for pixel (0, 0):

{
  r: 100,
  g: 150,
  b: 200,
  a: 255
}

fill(offsetX, offsetY, widht, height, color)

Fill region with passed color. Modifies current image.

Arguments:

• offsetX - horizontal offset from the left side of the image
• offsetY - vertical offset from the top side of the image
• width - region width
• height - region height
• color - color as {r,g,b,a} object or as a '#XXXXXX' string

Returns: current image object

Throws if region is not inside the current image

img
  .fill(0, 0, 16, 16, '#00ffFF') // fill with cyan
  .fill(16, 16, 16, 16, {r: 0, g: 255, b: 255, a: 127}); // fill with half-transparent cyan

set(x, y, color)

Same as fill(x, y, 1, 1, color)

crop(offsetX, offsetY, widht, height)

Crop image. Modifies current image.

Arguments:

• offsetX - horizontal offset from the left side of the image
• offsetY - vertical offset from the top side of the image
• width - new width
• height - new height

Returns: current image object

Throws if new image is not inside the current image.

img
    .crop(0, 0, 16, 16)
    .crop(8, 8, 8, 8);

save(file, callback)

Save image to file. Asynchronous operation.

Arguments:

• file - path to file to save image
• callback - function with one argument (error). Will be called after save operation finish or on error.

Overwrites existing file.

img.save('path/to/file.png', function(error) {
    if(error) {
        console.error('Error:', error);
    } else {
        console.log('OK');
    }
});