[reportlab-users] Image - mask parameter - effect on screen vs printer ?

Richard Shea rshea at thecubagroup.com
Thu Feb 28 04:00:21 EST 2013


Hi - I have an image (details of which are shown below) which I'd like
to use in a Table so that the tables background colour is visible.

To do this I've identified the colour which is current background of the
image (229, 229, 229) and set the mask parameter on the corresponding
Image object to ['229', '229', '229', '229', '229', '229'] so that that
colour should become transparent.

I then set the relevant row in the table to have a BACKGROUND of
Color(float(229)/256, float(229)/256, float(229)/256).

(Yes I know what I'm doing appears to be nonsensical but bear with me !)

The result of this on the screen is very good indeed - the colour is
uniform across the width of the table cell including that part of the
cell which is covered by the image.

Here's the problem. When I print the PDF on some printers the area
behind the Image is a different colour than the rest of the cell. When I
print it on other printers as far as I can see the colour is seamless -
aaargh !

My question is : if you're seeing something different when you print
than when you view is there something obvious I should check/change or
is a situation that's previously unknown !

============================================================================
FOR THE CURIOUS:

In case anyone cares the reason I'm setting a background colour in an
image to be transparent and then setting
the underlying table cell colour to the 'same' colour is because when I
left the image alone and just put it into the
cell the other cells around it (with nominally the same colour as
background) had a different look - hence my rather
strange experiment with transperency. I hoped that doing what I'm doing
now might help the situation.

============================================================================
DETAILS OF IMAGE FILE IN USE:


Regarding the image mentioned above file the details as shown by
ImageMagick are as follows:

C:\bin\installed\ImageMagick\ImageMagick-6.7.9-6>identify.exe -verbose
"Z:\0000-20120529\WORK1-1600-981-5f370c2b-bf20-4748-85d7-4daa0920edce.PNG"
Image:
Z:\0000-20120529\WORK1-1600-981-5f370c2b-bf20-4748-85d7-4daa0920edce.PNG
Format: PNG (Portable Network Graphics)
Class: DirectClass
Geometry: 1600x981+0+0
Units: Undefined
Type: PaletteAlpha
Endianess: Undefined
Colorspace: sRGB
Depth: 8-bit
Channel depth:
red: 8-bit
green: 8-bit
blue: 8-bit
alpha: 1-bit
Channel statistics:
Red:
min: 0 (0)
max: 229 (0.898039)
mean: 222.882 (0.874048)
standard deviation: 33.2371 (0.130342)
kurtosis: 35.7207
skewness: -5.98468
Green:
min: 0 (0)
max: 229 (0.898039)
mean: 223.265 (0.875549)
standard deviation: 32.632 (0.127969)
kurtosis: 38.7714
skewness: -6.26897
Blue:
min: 0 (0)
max: 229 (0.898039)
mean: 223.552 (0.876675)
standard deviation: 32.3235 (0.126759)
kurtosis: 40.5713
skewness: -6.44554
Alpha:
min: 255 (1)
max: 255 (1)
mean: 255 (1)
standard deviation: 0 (0)
kurtosis: 0
skewness: 0
Image statistics:
Overall:
min: 0 (0)
max: 229 (0.898039)
mean: 167.425 (0.656568)
standard deviation: 28.3476 (0.111167)
kurtosis: 334.13
skewness: -47.0674
Colors: 17
Histogram:
26965: ( 0, 0, 0,255) #000000 black
4603: ( 33, 33, 33,255) #212121 grey13
824: ( 54, 54, 54,255) #363636 grey21
513: ( 73, 73, 73,255) #494949 srgba(73,73,73,1)
467: ( 89, 89, 89,255) #595959 grey35
183: (104,104,104,255) #686868 srgba(104,104,104,1)
410: (119,119,119,255) #777777 srgba(119,119,119,1)
255: (133,133,133,255) #858585 grey52
430: (146,146,146,255) #929292 srgba(146,146,146,1)
53: (159,159,159,255) #9F9F9F srgba(159,159,159,1)
30035: (161,181,196,255) #A1B5C4 srgba(161,181,196,1)
339: (172,172,172,255) #ACACAC srgba(172,172,172,1)
490: (183,183,183,255) #B7B7B7 srgba(183,183,183,1)
210: (195,195,195,255) #C3C3C3 srgba(195,195,195,1)
512: (207,207,207,255) #CFCFCF grey81
88: (218,218,218,255) #DADADA srgba(218,218,218,1)
1503223: (229,229,229,255) #E5E5E5 grey90
Rendering intent: Perceptual
Gamma: 0.45455
Chromaticity:
red primary: (0.64,0.33)
green primary: (0.3,0.6)
blue primary: (0.15,0.06)
white point: (0.3127,0.329)
Interlace: None
Background color: white
Border color: srgba(223,223,223,1)
Matte color: grey74
Transparent color: none
Compose: Over
Page geometry: 1600x981+0+0
Dispose: Undefined
Iterations: 0
Compression: Zip
Orientation: Undefined
Properties:
date:create: 2013-02-28T11:38:28+13:00
date:modify: 2013-02-27T05:00:12+13:00
png:cHRM : chunk was found (see Chromaticity, above)
png:gAMA : gamma=0.45454544 (See Gamma, above)
png:IHDR.bit_depth : 8
png:IHDR.color_type : 6 (RGBA)
png:IHDR.interlace_method: 0 (Not interlaced)
png:IHDR.width,height : 1600, 981
png:sRGB : intent=0 (Perceptual Intent)
signature:
3640d77a9be3df74feaf44d1485fc295fada1312d54fece3ca6230965775beaa
Artifacts:
filename:
Z:\0000-20120529\WORK1-1600-981-5f370c2b-bf20-4748-85d7-4daa0920edce.PNG
verbose: true
Tainted: False
Filesize: 70.7KB
Number pixels: 1.57M
Pixels per second: 14.81MB
User time: 0.031u
Elapsed time: 0:01.106
Version: ImageMagick 6.7.9-6 2012-09-13 Q16 http://www.imagemagick.org

C:\bin\installed\ImageMagick\ImageMagick-6.7.9-6>



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