[OpenJDK 2D-Dev] [11] RFR JDK-7031957: DIB header of type BITMAPV2INFOHEADER & BITMAPV3INFOHEADER is not supported in BMPImageReader

[Jayathirth D V]

HI Phil,

 

Please find my observation:

In case of DIB header type BITMAPINFOHEADER/ BITMAPV4HEADER/ BITMAPV5HEADER, Microsoft documentation(https://msdn.microsoft.com/en-us/library/dd183376(v=vs.85).aspx ) mentions that mask values are valid only when compression type is BI_BITFIELDS. When compression type is BI_RGB which ii no compression, Microsoft document mentions that

 

1)      For 16 bpp : "The relative intensities of red, green, and blue are represented with five bits for each color component. The value for blue is in the least significant five bits, followed by five bits each for green and red. The most significant bit is not used.". So basically it should be RGB555.

2)      For 32 bpp : "Each DWORD in the bitmap array represents the relative intensities of blue, green, and red for a pixel. The value for blue is in the least significant 8 bits, followed by 8 bits each for green and red. The high byte in each DWORD is not used". So basically it should be XRGB8888.

 

This is why we have redMask = 0x7C00, greenMask = 0x3E0, blueMask = 0x1F in case of 16bpp and redMask   = 0x00FF0000, greenMask = 0x0000FF00, blueMask  = 0x000000FFfor 32bpp for all the three standard formats BITMAPINFOHEADER, BITMAPV4HEADER and BITMAPV5HEADER.

 

Since BITMAPV2INFOHEADER & BITMAPV3INFOHEADER support falls in between that of other Microsoft documented DIB header types it is good that we follow the same approach in case of BITMAPV2INFOHEADER & BITMAPV3INFOHEADER also.

 

Please let us know your inputs.

 

Thanks,

Jay

 

From: Phil Race 
Sent: Monday, March 19, 2018 11:07 PM
To: Jayathirth D V; 2d-dev
Subject: Re: [OpenJDK 2D-Dev] [11] RFR JDK-7031957: DIB header of type BITMAPV2INFOHEADER & BITMAPV3INFOHEADER is not supported in BMPImageReader

 

Since the principal addition of these formats is to add explicit fields
for supporting the bitmasks for accessing R/G/B/A it seems odd to
see there is code like this which ignores it when the data is uncompressed
by using these hardcoded values :

 456                             if ((int)compression == BI_RGB) {
 457                                 redMask = 0x7C00;
 458                                 greenMask = 0x3E0;
 459                                 blueMask = 0x1F;


I do see that it seems likely you copied this from the 108/124 case
but I'd like to see some proof that this is correct.


-phil.

On 03/14/2018 03:39 AM, Jayathirth D V wrote:

Hello All,

 

Please review the following solution in JDK11 :

 

Bug : https://bugs.openjdk.java.net/browse/JDK-7031957 

Webrev : HYPERLINK "http://cr.openjdk.java.net/%7Ejdv/7031957/webrev.00/"http://cr.openjdk.java.net/~jdv/7031957/webrev.00/ 

 

Issue: If we try to read any BMP image of DIB header type BITMAPV2INFOHEADER/ BITMAPV3INFOHEADER, we get IOException mentioning the BMP image type in not yet implemented.

 

Root cause:  BMPImageReader doesn't support DIB header types BITMAPV2INFOHEADER/ BITMAPV3INFOHEADER we support only BITMAPCOREHEADER, BITMAPINFOHEADER, BITMAPV4HEADER & BITMAPV5HEADER.

 

Solution: Many other tools like GIMP, Microsoft PowerPoint, IrfanView support BITMAPV2INFOHEADER & BITMAPV3INFOHEADER format BMP images. We can consider BITMAPV2INFOHEADER & BITMAPV3INFOHEADER header types having functionality in between that of BITMAPINFOHEADER & BITMAPV4HEADER. BITMAPINFOHEADER with type BITFIELDS & extra 4 bytes for alpha channel or First 56 bytes of BITMAPV4HEADER is nothing but BITMAPV3INFOHEADER.

 

To support BITMAPV2INFOHEADER & BITMAPV3INFOHEADER we can use similar approach of what we are doing while decoding first 56 bytes under BITMAPV4HEADER. So I have added additional "if()" to do the same, we can merge decoding of BITMAPV2INFOHEADER & BITMAPV3INFOHEADER at the same place where we are decoding BITMAPV4HEADER but we need to add many branch conditions to follow that approach.

 

Thanks,

Jay

 

 
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mail.openjdk.java.net/pipermail/2d-dev/attachments/20180320/2e4eaaa4/attachment-0001.html>