PNG IDAT specification I'm going over the W3 PNG specification (creating a PNG library from scratch) and I've finally found how to create a green 1x1 image.

Now I'm trying to create a bigger image of mixed Red, Green and Blue pixels. Let's say a 4x4 image. Sadly I'm getting all the pixels mixed and some of them are Black or Pink.

Details:


Signature: OK
IHDR: OK

Width: 4   
Heigh: 4 
Bit depth: 8
Color: 2
Filter: 0
Compression: 0
Interlace: 0

IDATA: 4 chunks*
IEND: OK


*IDATA chunks:


4 bytes length: Number of bytes of the DATA after Zlib deflate
4*1 byte type: IDAT 
X bytes data: 4*4bytes unsigned integers, Zlib deflated, one after the other, Network byte order 

255 for blue**
65280 for green** 
16711680 for red**

4 bytes crc: OK 


**Bitwise results of:

alpha&lt;&lt;24 | red&lt;&lt;16 | green&lt;&lt;8 | blue


With alpha, blue, green and red taking values from 0 to 255 

What's wrong with this?
I just answered this in Stack Overflow.  Here's the answer again:

The PNG pixels are in RGBA order, not ARGB, so you'd need to write

alpha | red&lt;&lt;24 | green &lt;&lt; 16 | blue &lt;&lt;8


But you are writing color type 2, so your pixels should be 3 bytes each instead of four; you can't really encode them in 4-byte integers as you've done. So either change the color type to 6 or switch to writing each sample as an individual byte.

Also you need a filter byte at the beginning of each row. Zero will work for you. So in your example 4x4 RGB image you will need to write 13 bytes per row

0 R G B R G B R G B R G B
0 R G B R G B R G B R G B
0 R G B R G B R G B R G B
0 R G B R G B R G B R G B


and zlib-compress that. It can all go into one IDAT chunk. If you need to write smaller IDAT chunks, you have to zlib-compress the image first, then split the zlib output into pieces that you put in consecutive IDAT chunks.