image/png: support custom zlib compression levels

[LukeMauldin]

In Go 1.3 there is no way to specify the zlib encoding level when writing a png image.

Request a new function, png.EncodeLevel(w io.Writer, m image.Image, level int) be added.
 The level could then be passed to zlib.NewWriter in image/png/writer.go:259

[minux]

Comment 1:

Labels changed: added release-none, repo-main.

[bradfitz]

Comment 2:

EncodeLevel is too specific and not future-proof.
I'd rather see:
package png
type Encoder struct {
    Level int
    .... future ...
}
func (e *Encoder) Encoder(w io.Writer, m image.Image) error {
    ...
}

[LukeMauldin]

Comment 3:

Sounds good to me

[gopherbot]

Comment 4:

CL https://golang.org/cl/129190043 mentions this issue.

[nigeltao]

Comment 5:

This issue was closed by revision 98e5a44.

Status changed to Fixed.