Joey@still_Learning.invalid
5/22/2014 2:56:00 AM
JJ wrote:
>On Wed, 21 May 2014 17:17:21 -0700, Joey@still_Learning.invalid wrote:
>> I'm trying to specify a group of colors as RGBa, but I'm lost.
>>
>> Example code:
>>
>> highlight_color = new Array(255,0,0);
>>
>> for (var x = 0; x < width; x++) {
>> for (var y = 0; y < height; y++) {
>>
>> gray_avg = ctx.getImageData(x, y, 1, 1).data[0];
>>
>> if (gray_avg >= threshold) { gray = highlight_color; }
>> ....
>> } }
>>
>> This works fine as shown, but I need to add the alpha channel to control
>> opacity. I've tried highlight_color = rgba(255,0,0,n) where 0<n<1, but it
>> throws an error. I've also tried =new Array(255,0,0,n) to no avail.
>> Please...what is the correct syntax?
>>
>> Thanks,
>
>The data property is an array of RGBA values. i.e.:
>[RR, GG, BB, AA, RR, GG, BB, AA, ...]
> ^ pixel #0 ^ pixel #1
>
>So, data[0] is the first pixel's red channel level, not the alpha channel.
>
>e.g.:
>
>var imgdata = ctx.getImageData(x, y, 1, 1).data;
>var red = imgdata[0];
>var green = imgdata[1];
>var blue = imgdata[2];
>var alpha = imgdata[3];
Thanks, JJ.
I failed to communicate my issue. I was simply looking for syntax, but no
matter. I found a much easier and better workaround using css3 opacity on
the canvas.
--
Joey