Hi Dif,
I found a way in new version of ImageMagick and Jmagick.
Version Details:
ImageMagick 6.8.9-7
JMagick 6.7.7
According to
http://www.w3.org/TR/PNG-Chunks.html
Color type is a single-byte integer that describes the interpretation of the image data. Color type codes represent sums of the following values: 1 (palette used), 2 (color used), and 4 (alpha channel used). Valid values are 0, 2, 3, 4, and 6.
Bit depth restrictions for each color type are imposed to simplify implementations and to prohibit combinations that do not compress well. Decoders must support all legal combinations of bit depth and color type. The allowed combinations are:
Color Allowed Interpretation
Type Bit Depths
0 1,2,4,8,16 Each pixel is a grayscale sample.
2 8,16 Each pixel is an R,G,B triple.
3 1,2,4,8 Each pixel is a palette index;
a PLTE chunk must appear.
4 8,16 Each pixel is a grayscale sample,
followed by an alpha sample.
6 8,16 Each pixel is an R,G,B triple,
followed by an alpha sample.
If we check ColorType and Bit Depth we can conclude that alpha is available.
We can get the colorType and Bit Depth from the Image :--