Question

I’m trying to create a new image using Image::Magick, and set the background color to an RGB value retrieved from a previous step. However, all that is being written out is a black image. I know the RGB values are correct, as I verified those. Below is an example of what I tried.

# Read RGB value at pixel 2,11 in another image
my $swatchImg = new Image::Magick;    
$swatchImg->Read($swatchPath)
my @rgb = $swatchImg->GetPixel(x=>2,y=>11); 
undef $swatchImg;   

# Create a new image, with the background set to the rgb value retrieved above 
my $img = Image::Magick->new;
$img->Set(size=>"50x50");
$img->Set(background=>\@rgb);
$img->ReadImage();

I’ve also tried:

$img->Colorize(fill=>\@rgb, opacity=>1);

Any ideas?

---

Edit:

This worked. Not sure if there is any cleaner approach:

ReadImage("xc:rgb(" . $rgb[0]*100 . "," . $rgb[1]*100 . "," . $rgb[2]*100 . ")")

Answer 1

You can do something like this:

my $rgbdec = $swatchImg->Get("pixel[2,11]");
my @rgbdec = split (/,/, $rgbdec);
my @rgbhex;
## Convert decimal @rgbdec (0..65536) to hex @rgbhex (00..FF)
for (my $i=0; $i<=3; $i++) {
    $rgbhex[$i] = sprintf("%X", $rgbdec[$i]/256); 
    if ($rgbhex[$i] eq "0") { $rgbhex[$i] = "00"; }
}
my $hexcolor = $rgbhex[0].$rgbhex[1].$rgbhex[2];

my $img = Image::Magick->new(size=>"50x50);
$img->Read("xc:#$hexcolor");

This assumes you are using ImageMagick with q-depth of 16 bits. If only 8 bits, then this:

    $rgbhex[$i] = sprintf("%X", $rgbdec[$i]/256); 

becomes this:

    $rgbhex[$i] = sprintf("%X", $rgbdec[$i]); 

Although I believe there is a simpler way to just use the decimal values in @rgbdec, perhaps someone will post that.