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    <p>Why are you using a timer at all? Why not just have a double for loop in your function that loops over all possible x- and y-coordinates in the image? Surely that would be waaaay faster than only checking at most 100 pixels per second. You would want to have the x (width) coordinates in the outer loop and the y (height) coordinates in the inner loop so that you are effectively scanning one column of pixels at a time from left to right, since you are trying to find the leftmost black pixel.</p> <p>Also, are you sure that each pixel in your image has a 4-byte (Uint32) representation? A standard bitmap would have 3 bytes per pixel. To check if a pixel is close to black, you would just examine each byte in the pixel separately and make sure they are all less than some threshold.</p> <p>EDIT: OK, since you are using UIGetScreenImage, I'm going to assume that it is 4-bytes per pixel.</p> <pre><code>const UInt8 *pixels = CFDataGetBytePtr(imageData); UInt8 blackThreshold = 10; // or some value close to 0 int bytesPerPixel = 4; for(int x = 0; x &lt; width1; x++) { for(int y = 0; y &lt; height1; y++) { int pixelStartIndex = (x + (y * width1)) * bytesPerPixel; UInt8 alphaVal = pixels[pixelStartIndex]; // can probably ignore this value UInt8 redVal = pixels[pixelStartIndex + 1]; UInt8 greenVal = pixels[pixelStartIndex + 2]; UInt8 blueVal = pixels[pixelStartIndex + 3]; if(redVal &lt; blackThreshold &amp;&amp; blueVal &lt; blackThreshold &amp;&amp; greenVal &lt; blackThreshold) { //This pixel is close to black...do something with it } } } </code></pre> <p>If it turns out that bytesPerPixel is 3, then change that value accordingly, remove the alphaVal from the for loop, and subtract 1 from the indices of the red, green, and blue values.</p> <p>Also, my current understanding is that UIGetScreenImage is considered a private function that Apple may or may not reject you for using.</p>
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    1. PODetect black pixel in image iOS
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    1. COHow can I change it to 3bit? The image is just a screenshot of a section on the screen that I captured using `CGImageRef UIGetScreenImage();` Also I'm completely open to not using the timer, I am not to familiar with while-infinite loops, I know how to set them up I just rarely use them so I guess I forgot haha. Also, is there a method to detect all pixels in the array and only return the x and y coordinates of those that are black rather than checking each one individually (even if I'm using a loop?)
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      1. USAlbert Renshaw
    2. COThere is nothing infinite about the loop, it just goes over the width and height of the image. One way or another you're going to have to check all of the pixels. There's no other way to figure out which one is black. Give me a second and I'll update my post with some code.
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    3. COAwesome code! Thankyou! And sorry I was thinking of the loop that is like while i<(i+1) { i++; } I dunno haha! It's been forever since I've done a loop I always use if else statements /: Thanks for the code though! let me test it!
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