JPEG Repair |
Table of Contents |
JPEG compression separates
an image into 8x8 (pixel) rectangles, then independently compresses each
rectangle. The result of a poor use of JPEG compression is an ugly, repetitive
pattern of blocks. Over-compression can take place when an image is saved
as a JPEG in computer software, like Photoshop, or when an image is snapped
at low-resolution in hardware, like a digital camera. JPEG Repair reduces
the damage caused by over-compressing screen-resolution JPEG image files,
making damaged images more aesthetically pleasing. Note: It is impossible to restore details from the original uncompressed imagedetails that were lost in the compression process. JPEG Repair reduces the visual impact of over-compression. Before After This chapter contains the following sections: Using JPEG RepairUse the following procedure to use JPEG Repair: 1. Select the area to be repaired. 2. Starting from the lowest setting, increment the Remove Artifacts slider until the perceptible blocky defects of JPEG compression have been removed. Do not overuse. 3. If even the strongest Remove Artifacts settings do not remove all of the blocky artifacts, use just enough Blur Edges to remove the remaining artifacts. 4. Use the Add Grain slider to add back any surface detail lost during Steps 2 and 3. Use only as much grain as needed. Slider and Button DescriptionsRemove ArtifactsThis slider controls
the strength of deblocking in JPEG Repairthe reduction
of rectangle-shaped artifacts in highly compressed JPEGs. Moving the slider
to the right strengthens the deblocking effect. You might assume that
selecting the highest value would give you the best results. This, however,
is not the case. Excessive Remove Artifacts values result
in an unnaturally soft appearance in your image. Dont smear too
much Vaseline on the lens. Use only as much artifact removal as necessary. Blur EdgesThis slider controls
the amount of blur apparent on the discrete edges within your selection.
Moving the slider to the right increases the amount of blur applied. Some
blur can help wipe out defects, such as extra stubborn artifact edges.
Too much can wipe out all detail from your image. Use Blur Edges cautiously. Add GrainJPEG Repair introduces
subtle, organic noiserandomly placed blobs in your image or selection
that help recreate the organic surface textures of higher-resolution,
un-compressed images. Moving the slider to the right yields a stronger
pattern of dark blobs. Again, only use as much as needed to get the best
results. Randomize GrainTo instantly change the arrangement of grain added to your selection, click this button. If the Add Grain slider is set to 0, the Randomize Grain button is disabled. TutorialsUsing Multiple Selections to Repair a JPEGSometimes, JPEG compression artifacts seem perceptibly stronger in different areas within an image. It is best to separately select and filter these areas. By treating all damaged areas the same, you risk losing detail in the less damaged areas of your image. Use the following procedure to get the best results when using multiple selections. 1. Identify the areas of your image containing visually similar damage. The image below provides a simple example of how damage can look different in parts of an image. In this picture, the yolks exhibit more damage than the whites. 2. Select one of the visually similar areas. 3. Perform JPEG Repair on this selection and click OK. 4. Repeat steps 2 and 3 until you have removed the JPEG artifacts from your image. Tips and Tricks
|