# pngspark
### [Sparklines](https://github.com/holman/spark) as PNGs

![histogram](https://cloud.githubusercontent.com/assets/95347/6131872/f78ab708-b11c-11e4-9ae2-fd6cd0ec2b76.png)

Uses [LuPng](https://github.com/jansol/LuPng).

## Install
```
make
[sudo] make install [PREFIX=/usr/local]
```

## Usage
```
echo 1 2 3 ... | pngspark [-h height] [-c color] [-s scaling] output.png
```

### Options
* `-h height`: the height of the image in pixels
* `-c color`: the color of the foreground, as #rrggbb hex
* `-s scaling`: scaling factor. 0 to keep things proportional, 1 to make the
  minimum value be at the bottom of the image

## Examples

Display BTC ticker data
```sh
curl -s https://api.bitcoinaverage.com/history/USD/per_minute_24h_sliding_window.csv | sed 1d | cut -d, -f2 | ./pngspark -o btc.png -s 0.995 -h 80 -c 0066cc
```
![btc](https://cloud.githubusercontent.com/assets/95347/6131571/ed7005c2-b11a-11e4-837c-58b07cd5a9c3.png)

Show a sine wave
```sh
seq 1 720 | awk '{print sin($1/30)}' | ./pngspark -o sine.png -h 30 -c 33c011
```
![sine](https://cloud.githubusercontent.com/assets/95347/6132308/b42da1d4-b11f-11e4-9748-5b61febd9df9.png)

## API

Generate pngsparks in your own C programs!

All int methods return 0 on success and nonzero on failure.

```c
struct pngspark;
```
A png spark instance: collection of values and settings.

```c
int pngspark_init(struct pngspark *ps, size_t height, const char *color, double scaling);
```
Initialize a pngspark struct. Arguments are as in the command-line options.

```c
int pngspark_append(struct pngspark *ps, double value);
```
Append a value to the pngspark.

```c
int pngspark_write(struct pngspark *ps, FILE *file);
```
Process the values and write as a PNG to a file.

```c
void pngspark_end(struct pngspark *ps);
```
Release allocated memory for the values of the pngspark. (Does not free `ps`, however).

## License

MIT