Databases
StackOverflow2013
Postsdbo
PO
 

Note that there are some explanatory texts on larger screens.

plurals
  1. PO
    primarykey
    data
    text
    <p>I'm not aware of any accessible built-in way to convert a biplanar Y / CbCr image to RGB in iOS. However you should be able to perform the conversion yourself in software, e.g.</p> <pre><code>uint8_t clamp(int16_t input) { // clamp negative numbers to 0; assumes signed shifts // (a valid assumption on iOS) input &amp;= ~(num &gt;&gt; 16); // clamp numbers greater than 255 to 255; the accumulation // of the mask looks odd but is an attempt to avoid // pipeline stalls uint8_t saturationMask = num &gt;&gt; 8; saturationMask |= saturationMask &lt;&lt; 4; saturationMask |= saturationMask &lt;&lt; 2; saturationMask |= saturationMask &lt;&lt; 1; num |= saturationMask; return num&amp;0xff; } ... CVPixelBufferLockBaseAddress(imageBuffer, 0); size_t width = CVPixelBufferGetWidth(imageBuffer); size_t height = CVPixelBufferGetHeight(imageBuffer); uint8_t *baseAddress = CVPixelBufferGetBaseAddress(imageBuffer); CVPlanarPixelBufferInfo_YCbCrBiPlanar *bufferInfo = (CVPlanarPixelBufferInfo_YCbCrBiPlanar *)baseAddress; NSUInteger yOffset = EndianU32_BtoN(bufferInfo-&gt;componentInfoY.offset); NSUInteger yPitch = EndianU32_BtoN(bufferInfo-&gt;componentInfoY.rowBytes); NSUInteger cbCrOffset = EndianU32_BtoN(bufferInfo-&gt;componentInfoCbCr.offset); NSUInteger cbCrPitch = EndianU32_BtoN(bufferInfo-&gt;componentInfoCbCr.rowBytes); uint8_t *rgbBuffer = malloc(width * height * 3); uint8_t *yBuffer = baseAddress + yOffset; uint8_t *cbCrBuffer = baseAddress + cbCrOffset; for(int y = 0; y &lt; height; y++) { uint8_t *rgbBufferLine = &amp;rgbBuffer[y * width * 3]; uint8_t *yBufferLine = &amp;yBuffer[y * yPitch]; uint8_t *cbCrBufferLine = &amp;cbCrBuffer[(y &gt;&gt; 1) * cbCrPitch]; for(int x = 0; x &lt; width; x++) { // from ITU-R BT.601, rounded to integers uint8_t y = yBufferLine[x] - 16; uint8_t cb = cbCrBufferLine[x &amp; ~1] - 128; uint8_t cr = cbCrBufferLine[x | 1] - 128; uint8_t *rgbOutput = &amp;rgbBufferLine[x*3]; rgbOutput[0] = clamp(((298 * y + 409 * cr - 223) &gt;&gt; 8) - 223); rgbOutput[1] = clamp(((298 * y - 100 * cb - 208 * cr + 136) &gt;&gt; 8) + 136); rgbOutput[2] = clamp(((298 * y + 516 * cb - 277) &gt;&gt; 8) - 277); } } </code></pre> <p>Just written directly into this box and untested, I think I've got the cb/cr extraction correct. You'd then use <code>CGBitmapContextCreate</code> with <code>rgbBuffer</code> to create a <code>CGImage</code> and hence a <code>UIImage</code>.</p>
    singulars
    1. This table or related slice is empty.
    1. POkCVPixelFormatType_420YpCbCr8BiPlanarFullRange frame to UIImage conversion
      singulars
      1. PTQuestion
    1. PTAnswer
    1. USRobert
    1. USTommy
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    3. VO
      singulars
      1. PO
      1. This table or related slice is empty.
      1. VTUpMod
    1. COThe conversion to RGB is just an intermediate step, yes. The problem with your solution is that this API is not available in iOS 5.0. There is a method called imageWithCVPixelBuffer that I could use instead, but as my original format is biplanar, I have two pixel buffers. :-( Thanks anyway!
      singulars
      1. PO
      1. USzapador
    2. COSorry; I stupidly loaded the wrong page in Safari and was sitting there looking at the OS X documentation for CIImage rather than the iOS. I'll write a new answer.
      singulars
      1. PO
      1. USTommy
    3. COTommy, thank you for your code. It works like a champ with a few changes. I would like to vote up for you but I dont have enough reputation.
      singulars
      1. PO
      1. USzapador
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload