This module alpha-composites images of the same size and returns the compressed image.
var blend = require('blend');
var image1; // Contains a compressed PNG image as a buffer.
var image2;
blend([ image1, image2 ], function(err, result) {
// result contains the blended result image compressed as PNG.
});
blend([ image1, image2 ], {
format: 'jpeg',
quality: 90
}, function(err, result) {
// result contains the blended result image compressed as JPEG.
});
format
:jpeg
orpng
quality
: integer indicating the quality of the final image. Meaning and range differs per format. For JPEG range is from 0-100. It defaults to 80. The lower the number the lower image quality and smaller the final image size. For PNG range is from 2-256. It means the # of colors to reduce the image to using. The lower the number the lower image quality and smaller the final image size.width
: integer, default 0: final width of blended image. If options provided with no width value it will default to 0height
: integer, default 0: final width of blended image. If options provided with no height value it will default to 0reencode
: boolean, default falsematte
: when alpha is used this is the color to initialize the buffer to (reencode will be set to true automatically when a matte is supplied)compression
: level of compression to use when format ispng
. The higher value indicates higher compression and implies slower encodeing speeds. The lower value indicates faster encoding but larger final images. Default is 6. If the encoder islibpng
then the valid range is between 1 and 9. If the encoder isminiz
then the valid range is between 1 and 10. The reason for this difference is thatminiz
has a special "UBER" compression mode that tries to be extremely small at the potential cost of being extremely slow.palette
: pass a blend.Palette object to be used to reduced PNG images to a fixed array of colorsmode
:octree
orhextree
- the PNG quantization method to use, from Mapnik: https://github.com/mapnik/mapnik/wiki/OutputFormats. Octree only support a few alpha levels, but is faster while Hextree supports many alpha levels.encoder
:libpng
orminiz
- the PNG encoder to use.libpng
is standard whileminiz
is experimental but faster.
To compile, this module requires libjpeg
and libpng
.
Both /usr and /usr/local with be searched for these dependencies by default.
On Ubuntu, type sudo apt-get install libjpeg8-dev libpng12-dev
to install them.
Mac OS X ships with png at /usr/X11, which will also be searched.
If you have jpeg or png installed in a custom location you can do:
./configure --with-jpeg=/opt/jpeg --with-png=/opt/png
To run tests for this module, run npm install --dev
to install the testing framework, then
npm test
. Tests require Imagemagick for its compare
utility.