Re: Width, Height, and Rowbytes in FxImage returning possible wrong values.
Re: Width, Height, and Rowbytes in FxImage returning possible wrong values.
- Subject: Re: Width, Height, and Rowbytes in FxImage returning possible wrong values.
- From: Brad Wright <email@hidden>
- Date: Sun, 10 Aug 2008 22:22:53 -0700
Hi Darrin:
If it was two rows stacked in a single rowBytes, I'd see a different
pattern in the image. In this case the image suppose to be 720 wide,
but the actual pattern in the bytes shows that it 1440 wide. The
width and height are inconsistent with what is actually contained in
the image. It's reporting 720x240 in the FxImage for width and
height, but actual contents the memory is consistent with 1440 wide.
To test this, I ran a color bar test pattern across the image and the
memory pattern is consistent with 1440 wide. If it were double
stacked in a rowBytes you'd see a duplication of color bar
information. In this case, I'm only seeing a 1/2 of the color bar
pattern in the first 720 pixels. If it were row 1 and row 2, the
entire color bar pattern would be contained in the first 720 pixels
and it would repeat in the next 720 pixels for the next row. This
isn't the case as far as I can tell.
Brad
On Aug 10, 2008, at 9:46 PM, Darrin Cardani wrote:
Brad,
What is the field order of the images you are receiving? What are
the width and height? Steve's analysis is correct. FCP will often
point you to a bitmap which is as many bytes wide as 2 scan lines,
one of which is an even field and one of which is an odd field.
Darrin
On Aug 10, 2008, at 9:41 PM, Brad Wright wrote:
Thanksi Steve:
Actually, I did some analysis on the image being returned. I
actually walk the image a for loop and the values are consistent
with a 1440x1080 image. I did this by running creating test
patterns for the image, so I can see where the values should line
up in memory. In this particular case, the values are consistent
with 1440 pixels wide and not 720. I'm testing with Final Cut
5.14 and the latest FxPlug API's. It certainly could be broken in
this combination.
Brad Wright
On Aug 10, 2008, at 9:15 PM, Steve Christensen wrote:
No, you're assuming that 16 x width == rowBytes. That's not
always true.
What I was getting at was this: 23040 bytes works out to 1440 16-
byte float pixels between the start of each succeeding row. Given
that you're seeing an image size of 720 x 240 (half of 720 x
480), it looks like you have imageInfo.fieldOrder set to either
kFxFieldOrder_UPPER_FIRST or kFxFieldOrder_LOWER_FIRST. (This is
also likely the type of input and output images your plugin is
being provided.) Thus the bitmap is laid out like this:
|<- 16 x width ->||<- 16 x width ->|
|<----------- rowBytes ----------->|
row 0 |<---- upper --->||<--- lower ---->|
row 1 |<---- upper --->||<--- lower ---->|
...
row 719 |<---- upper --->||<--- lower ---->|
or this:
|<- 16 x width ->||<- 16 x width ->|
|<----------- rowBytes ----------->|
|<--- upper ---->|
row 0 |<---- lower --->||<--- upper ---->|
row 1 |<---- lower --->||<--- upper ---->|
...
row 719 |<---- lower --->||<--- upper ---->|
The rowBytes value is set so that you're using every other line
(or one field) of the overall image. You should only be working
with the first 720 pixels (or 11520 bytes) on each line since the
other half of the rowBytes -may- contain the other field's pixels
or it may be uninitialized -- the implementation details are
unspecified. That's why you have to respect both the image
dimensions as well as the rowBytes: there may be bytes at the end
of each row in the image you're processing that are supposed to
be left alone.
On Aug 10, 2008, at 8:20 PM, Brad Wright wrote:
Thanks Steve:
From what I'm seeing math doesn't quite add up. The row bytes
reports 23040 while the image format is 32 bit float. 32 bit
float is 16 bytes wide. Therefore, 23040/16 is 1440 which is
the width of the sequence settings. So, it looks like something
is inconsistent.
Brad
On Aug 9, 2008, at 11:45 PM, Steve Christensen wrote:
What value did you supply in imageInfo.fieldOrder? If it
contains something other than kFxFieldOrder_PROGRESSIVE, the
bitmap may actually contain the entire image, but rowBytes is
set up so you only see the pixels in every other row. If that's
the case, it's not an application bug since it's doing exactly
what you told it to do.
On Aug 9, 2008, at 6:29 PM, Brad Wright wrote:
I'm seeing possibly wrong values for width and height in an
FxImage. The problem happens when I export to a DVC Pro 25
NTSC movie from an HD timeline. My sequence is 1440x1080, and
the exported image is 720x480. In the rederOutput function I
retrieve the actual image using the temporal image API.
if ([tempororalImageApi getInputBitmap:(FxBitmap **)
&myBitmapImage withInfo:(FxRenderInfo) imageInfo atTime:
(double) renderInfo.frame]==NO)
{
NSLog(@"Failed to retrieve the original Bitmap image\n");
return NO;
}
Here's the values I get:
[myBitmapImage width] == 720
[myBitmapImage height] == 240
[myBitmapImage rowBytes] = 23040
The image format is Float and 32 bit wide.
23040 is the correct row bytes value for the image if it's at
1440 pixels wide.
When I try to process the image using these values in my loop,
I get only the first part of the actual image. So it appears
that the image is actually 1440 wide instead of being 720
wide. Is this a know bug? Is there a workaround?
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| References: | |
| | >Width, Height, and Rowbytes in FxImage returning possible wrong values. (From: Brad Wright <email@hidden>) |
| | >Re: Width, Height, and Rowbytes in FxImage returning possible wrong values. (From: Steve Christensen <email@hidden>) |
| | >Re: Width, Height, and Rowbytes in FxImage returning possible wrong values. (From: Brad Wright <email@hidden>) |
| | >Re: Width, Height, and Rowbytes in FxImage returning possible wrong values. (From: Steve Christensen <email@hidden>) |
| | >Re: Width, Height, and Rowbytes in FxImage returning possible wrong values. (From: Brad Wright <email@hidden>) |
| | >Re: Width, Height, and Rowbytes in FxImage returning possible wrong values. (From: Darrin Cardani <email@hidden>) |