Summary of the PNG standard chunks

Name Multiplicity Ordering

IHDR     1        First
PLTE     0-1      Before IDAT
IDAT     1+       Multiple IDATs are consecutive
IEND     1        Last

cHRM     0-1      Before PLTE and IDAT
gAMA     0-1      Before PLTE and IDAT
iCCP     0-1      Before PLTE and IDAT
sBIT     0-1      Before PLTE and IDAT
sRGB     0-1      Before PLTE and IDAT
bKGD     0-1      After PLTE; before IDAT
hIST     0-1      After PLTE; before IDAT
tRNS     0-1      After PLTE; before IDAT
pHYs     0-1      Before IDAT
sPLT     0+       Before IDAT
tIME     0+       None
iTXt     0+       None
tEXt     0+       None
zTXt     0+       None