当至少其中一个没有值时，使用php从图像中查找红色，绿色和蓝色数组的最大值

Question

I'm working on a project that involves extracting Red, green and blue values from an image and finding the maximum value of red values, green values and blue values. When I upload an image that doesn't contain red values I got this error message: Undefined offset. The same message appears if image doesn't contain green or blue values. I used empty() to check if array is empty but it didn't help.

my code:

for($j1=0;$j1<=$red_count;$j1++){
    if (empty($reds)){
        $reds[$j1]=0;
    }
    if ($reds[$j1]>=$red_max){
        $red_max = $reds[$j1];
    }   
}

for($j2=0;$j2<=$blue_count;$j2++){
    if (empty($blues)){
        $blues[$j2]=0;
    }
    if ($blues[$j2]>=$blue_max){
        $blue_max = $blues[$j2];
    }
}

for($j3=0;$j3<=$green_count;$j3++){
    if (empty($greens)){
        $greens[$j3]=0;
    }
    if ($greens[$j3]>=$green_max){
        $green_max = $greens[$j3];
    }
}

Answer 1

Let's just look at one color. The problem is your for-loop. Because it is run once, even if $reds is empty. (And it's run on time to often.) Why not use foreach?

$red_max = 0; //initialize
foreach ($reds as $value) {
    if ($value > $red_max) { $red_max = $value; }
}

I guess you can apply this for the different colors.