<AWT Dev> [11] JDK-8169187: [macosx] Aqua: java/awt/image/multiresolution/MultiresolutionIconTest.java

shashidhara.veerabhadraiah at oracle.com shashidhara.veerabhadraiah at oracle.com
Sat May 12 16:15:59 UTC 2018

Hi Sergey, I read that slightly different. The getPixelColor() would not 
be accurate but createScreenCapture() works differently but advantageous 
to us. The reason for that is that if we have a HiDpi factor screen of 
say 3, then actually 3 sub pixels forms each particular location. The 
getPixelColor() would always choose the first pixel(0th) whereas 
createScreenCapture() since it converts to low res image using the 
nearest neighbor, it would choose the color of the most nearest point 
for that particular location.

We don't need the information of the 3 pixel color info but since the 
limitation of getPixelColor() is that it can return only one color and 
that color should actually be closest to that particular location. But 
instead we always return the first pixel color. On the other hand, 
createScreenCapture() would choose the closest pixel out of the 3 pixel 
color info, which is required in our case.

This is what I felt out of the 2 ways, please let me know what do you 
think of this.

Thanks and regards,


On 12/05/18 4:38 AM, Sergey Bylokhov wrote:
> Hi, Shashi.
> It means that the updated test will not trust getPixelColor() which 
> returns exact color which is drawn on the screen, but will trust 
> createScreenCapture() which will apply transformation of the actual 
> color. This looks odd.
> On 11/05/2018 00:45, shashidhara.veerabhadraiah at oracle.com wrote:
>> 1. In this case we will be using the low resolution variant of the 
>> image that was captured.
>> 2. The low resolution variant was created from the high resolution 
>> image that was actually captured from an high res display. This is 
>> done using the nearest neighbor interpolation which actually chooses 
>> the most nearest point's value and ignores the other points values 
>> completely.
>> This may be a reason to get a different color for the said pixel.
>> By using the getPixelColor():
>> 1. This calls the getRGBPixel().
>> 2. Here we return only the 0th pixel color ignoring the scaling 
>> effect in the case of hidpi display units, where there may be many 
>> sub pixels for the given user space coordinates.
>> This may be the reason for getting failed here.
>> Thanks and regards,
>> Shashi
>> On 11/05/18 2:39 AM, Sergey Bylokhov wrote:
>>> Hi, Shashi.
>>> On 10/05/2018 08:40, Shashidhara Veerabhadraiah wrote:
>>>> The test was failing because of the color value mismatches, the fix 
>>>> is to get an image of the part of the window for which color needs 
>>>> to be fetched from the image pixel.
>>> Can you please clarify why r.getPixelColor(x, y) returns incorrect 
>>> color and r.createScreenCapture(bouns{x,y,1,1}) will work, since 
>>> internally both of these methods are use the same method 
>>> CRobot.getRGBPixels()

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