Yeah then it sounds like the same limitation of image sizes apply to the text.
Know iOS Resource Limits
Because of the memory available on iOS, there are limits on the number of resources it can process:
The maximum size for decoded GIF, PNG, and TIFF images is 3 megapixels for devices with less than 256 MB RAM and 5 megapixels for devices with greater or equal than 256 MB RAM.
That is, ensure that width * height = 3 * 1024 * 1024 for devices with less than 256 MB RAM. Note that the decoded size is far larger than the encoded size of an image.
The maximum decoded image size for JPEG is 32 megapixels using subsampling.
JPEG images can be up to 32 megapixels due to subsampling, which allows JPEG images to decode to a size that has one sixteenth the number of pixels. JPEG images larger than 2 megapixels are subsampled—that is, decoded to a reduced size. JPEG subsampling allows the user to view images from the latest digital cameras.
The maximum size for a canvas element is 3 megapixels for devices with less than 256 MB RAM and 5 megapixels for devices with greater or equal than 256 MB RAM.
The height and width of a canvas object is 150 x 300 pixels if not specified.
If your script executes for more than 10 seconds, Safari on iOS stops executing the script at a random place in your code, so unintended consequences may result.
The maximum number of documents that can be open at once is eight on iPhone and nine on iPad.
In iOS 2.2.1 and earlier, the sum of all of the frames needs to be less than 2 megapixels—that is, width * height * number of frames = 2 * 1024 * 1024. In iOS 3.0 and later, the limit only applies to one frame at a time.
You also need to size images appropriately. Don’t rely on browser scaling. For example, don’t put a 100 x 100 image in a 10 x 10 <img> element. Tile small backgrounds images; don’t use large background images.