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https://github.com/britzl/defold-png
Defold native extension to load and save PNG images
https://github.com/britzl/defold-png
defold defold-library png
Last synced: about 1 month ago
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Defold native extension to load and save PNG images
- Host: GitHub
- URL: https://github.com/britzl/defold-png
- Owner: britzl
- License: mit
- Created: 2017-05-29T14:16:19.000Z (over 7 years ago)
- Default Branch: master
- Last Pushed: 2022-03-07T22:41:37.000Z (almost 3 years ago)
- Last Synced: 2024-11-02T14:33:48.318Z (about 2 months ago)
- Topics: defold, defold-library, png
- Language: C
- Size: 83 KB
- Stars: 19
- Watchers: 4
- Forks: 2
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE.md
Awesome Lists containing this project
- awesome-defold - defold-png
README
# defold-png
Defold native extension to load and save PNG images using [lodepng](https://github.com/lvandeve/lodepng).
## Installation
You can use defold-png in your own project by adding this project as a [Defold library dependency](https://www.defold.com/manuals/libraries/). Open your game.project file and in the dependencies field under project add:
https://github.com/britzl/defold-png/archive/master.zip
Or point to the ZIP file of a [specific release](https://github.com/britzl/defold-png/releases).
## Usage
#### png.decode_rgba(bytes, premultiply_alpha)
Decode a PNG into a [Defold buffer](https://www.defold.com/ref/buffer/) containing the raw RGBA pixel data of the PNG. If `premultiply_alpha` is true the alpha value of each pixel will be premultiplied into the RGB color values. This is needed when using the buffer to update a sprite texture or similar since the Defold engine uses premultiplied alpha internally. Once you have the buffer it's possible to get and manipulate the raw pixel data in Lua using `buffer.get_stream()` or set it as a texture on a sprite:
```
-- load a png from disk
local f = io.open("my.png", "rb")
local bytes = f:read("*a")
-- decode the png to RGBA buffer
local buf, w, h = png.decode_rgba(bytes, true)
-- change the texture on a sprite to the loaded png
local resource_path = go.get("#sprite", "texture0")
local header = { width = w, height = h, type = resource.TEXTURE_TYPE_2D, format = resource.TEXTURE_FORMAT_RGBA, num_mip_maps = 1 }
resource.set_texture(resource_path, header, buf)
```
#### png.decode_rgb(bytes)
Decode a PNG into a [Defold buffer](https://www.defold.com/ref/buffer/) containing the raw RGB pixel data of the PNG. Once you have the buffer it's possible to get and manipulate the raw pixel data in Lua using `buffer.get_stream()` or set it as a texture on a sprite:
```
-- load a png from disk
local f = io.open("my.png", "rb")
local bytes = f:read("*a")
-- decode the png to RGB buffer
local buf, w, h = png.decode_rgb(bytes)
-- change the texture on a sprite to the loaded png
local resource_path = go.get("#sprite", "texture0")
local header = { width = w, height = h, type = resource.TEXTURE_TYPE_2D, format = resource.TEXTURE_FORMAT_RGB, num_mip_maps = 1 }
resource.set_texture(resource_path, header, buf)
```
#### png.info(bytes)
Read the PNG header and return information about the PNG.
```
-- load a png from disk
local f = io.open("my.png", "rb")
local bytes = f:read("*a")
local info = png.info(bytes)
print(info.width)
print(info.height)
print(info.colortype)
print(info.bitdepth)
```
#### png.encode_rgb(pixels, width, height)
Encode raw RGB pixels to a PNG with the same color type.
```
-- create 100x100 red pixels
local w = 100
local h = 100
local pixels = string.rep(string.char(255,0,0), w * h)
-- encode
local bytes = png.encode_rgb(pixels, w, h)
-- save png to file
local f = io.open("my.png", "wb")
f:write(bytes)
f:flush()
f:close()
```
#### png.encode_rgba(pixels, width, height)
Encode raw RGBA pixels to a PNG with the same color type.
```
-- create 100x100 red pixels with 50% transparency
local w = 100
local h = 100
local pixels = string.rep(string.char(255,0,0, 128), w * h)
-- encode
local bytes = png.encode_rgba(pixels, w, h)
-- save png to file
local f = io.open("my.png", "wb")
f:write(bytes)
f:flush()
f:close()
```
#### png.RGB
Red, green and blue: rgb/truecolor
#### png.RGBA
Red, green, blue and alpha
#### png.GREY
Grayscale
#### png.GREY_ALPHA
Grayscale and alpha: level of opacity for each pixel
#### png.PALETTE
Indexed: channel containing indices into a palette of colors