Scale a PNG in Unity5? - Bountie - unity3d

Question

Surprisingly in Unity, for years the only way to simply scale an actual PNG is to use the very awesome library http://wiki.unity3d.com/index.php/TextureScale
Example below
How do you scale a PNG using Unity5 functions? There must be a way now with new UI and so on.
So, scaling actual pixels (such as in Color[]) or literally a PNG file, perhaps downloaded from the net.
(BTW if you're new to Unity, the Resize call is unrelated. It merely changes the size of an array.)
public WebCamTexture wct;
public void UseFamousLibraryToScale()
{
// take the photo. scale down to 256
// also crop to a central-square
WebCamTexture wct;
int oldW = wct.width; // NOTE example code assumes wider than high
int oldH = wct.height;
Texture2D photo = new Texture2D(oldW, oldH,
TextureFormat.ARGB32, false);
//consider WaitForEndOfFrame() before GetPixels
photo.SetPixels( 0,0,oldW,oldH, wct.GetPixels() );
photo.Apply();
int newH = 256;
int newW = Mathf.FloorToInt(
((float)newH/(float)oldH) * oldW );
// use a famous Unity library to scale
TextureScale.Bilinear(photo, newW,newH);
// crop to central square 256.256
int startAcross = (newW - 256)/2;
Color[] pix = photo.GetPixels(startAcross,0, 256,256);
photo = new Texture2D(256,256, TextureFormat.ARGB32, false);
photo.SetPixels(pix);
photo.Apply();
demoImage.texture = photo;
// consider WriteAllBytes(
// Application.persistentDataPath+"p.png",
// photo.EncodeToPNG()); etc
}
Just BTW it occurs to me I'm probably only talking about scaling down here (as you often have to do to post an image, create something on the fly or whatever.) I guess, there would not often be a need to scale up in size an image; it's pointless quality-wise.

Answer 1

If you're okay with stretch-scaling, actually there's simpler way by using a temporary RenderTexture and Graphics.Blit. If you need it to be Texture2D, swapping RenderTexture.active temporarily and read its pixels to Texture2D should do the trick. For example:
public Texture2D ScaleTexture(Texture src, int width, int height){
RenderTexture rt = RenderTexture.GetTemporary(width, height);
Graphics.Blit(src, rt);
RenderTexture currentActiveRT = RenderTexture.active;
RenderTexture.active = rt;
Texture2D tex = new Texture2D(rt.width,rt.height);
tex.ReadPixels(new Rect(0, 0, tex.width, tex.height), 0, 0);
tex.Apply();
RenderTexture.ReleaseTemporary(rt);
RenderTexture.active = currentActiveRT;
return tex;
}